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Re: An issue during expanding an cluster - one osd getting close to nearfull
by Robert Lukan 05 Jul '26

05 Jul '26

Thank you Eugen and Anthony for your comments. Expanding a cluster with one host with the same amount of disks as in other nodes worked perfectly fine. We also (unwantingly) made a test with expanding with one disk(osd) and we have crossed the near-full state. Also thank you for sharing some more details, it is really informative to get those insights into more corner case scenarios. I wish that Ceph documentation would have a few more guidelines, something similar to what Clyso has put together. Regards, Robert On Wed, 1 Jul 2026 at 15:07, Eugen Block via ceph-users <ceph-users(a)ceph.io> wrote: > Hi, > > I would try to avoid adding a host with only few OSDs if other hosts > are equipped differently. Although I haven't checked in a while I > don't expect the behavior to have changed in recent versions. > > So here's my theory: If you add a new host with only one or two OSDs, > Ceph can assign many more PGs than average to the first up OSD in > order to comply with failure domain (probably host). Same goes for the > last OSD during shut down. We had a related case four years ago when > we tried to rebuild OSD nodes in a customer cluster. Since the > customer cluster was still on default values for mon_max_pg_per_osd > and osd_max_pg_per_osd_hard_ratio, the (too many) assigned PGs led to > inactive PGs: > > > maybe_wait_for_max_pg withhold creation of pg 75.56s16: 750 >= 750 > > When more OSDs were created on that host (ceph-volume does that > sequentially), the issue resolved eventually, except for some inactive > PGs, failing the MGR resolved those as well. Since you have around 360 > PGs per OSD in average, I assume you increased mon_max_pg_per_osd > (default 250), maybe also osd_max_pg_per_osd_hard_ratio (default 3), > you most likely dodged the "inactive PG" bullet. > > So my recommendation would be to rather add the hosts with all OSDs at > the same time but with crush weight 0. That way you have time to > inspect the outcome (for example with dedicated DB/WAL devices you can > check if they were created according to the specs). Then reweight the > OSDs to the correct value, some users do that gradually to prevent an > overload. > > Note the recent discussion about osd heartbeats when adding multiple > hosts at once: > > > https://lists.ceph.io/hyperkitty/list/ceph-users@ceph.io/thread/RHVPS247M4E… > > Regards, > Eugen > > Zitat von Robert Lukan via ceph-users <ceph-users(a)ceph.io>: > > > Hi everyone, > > > > We are currently in the middle of migrating our infrastructure to a > > Proxmox/Ceph stack and ran into a concerning edge case while expanding > the > > cluster. I am hoping to get some advice on the safest way to handle this > > without risking a nearfull OSD. > > > > *The Topology & Situation:* > > > > *Existing:* 5 hosts (proxmox-01 to proxmox-05), each with 8x 7TB SSDs. > > > > *Expansion:* Added a new host (proxmox-08) with 2x 7TB SSDs (osd.40 and > > osd.41). > > > > *Cluster Average:* ~360 PGs per OSD, ~60% utilization. > > > > *Ceph Version:* Squid 19.2.3 > > > > The last time we were expanding the cluster, we had issues when expanding > > it with many OSDs at the same time(it was a memory problem on a host), so > > we decided to be more careful and add 2 disks at the time. > > > > During the backfill phase, we noticed osd.40 catching significantly more > > PGs than osd.41. We paused the migration by setting the nobackfill flag > to > > prevent a potential nearfull situation. > > > > *The Current State (ceph osd df):* > > > > osd.40: 423 PGs, 72.56% used, > > > > osd.41: 307 PGs, 51.87% used, > > > > We had 218 PGs sitting in active+remapped+backfill_wait. At that stage we > > have paused the backfill. > > > > If we were to unset nobackfill, the incoming data for those 218 PGs would > > risk pushing osd.40 past the 85% nearfull threshold. However, our > > balancer refused to generate any optimization plans. It reports: > > "optimize_result": > > "Unable to find further optimization... or distribution is already > perfect" > > > > We "understand" why this is happening: the balancer is evaluating only > when > > backfilling is done. However, it is completely ignoring the transient > acting > > state, which was heavily overloading osd.40 > > > > *Our Temporary Workaround:* To prevent the potential issue, we have > > temporarily set the reweight of osd.40 to 0 (effectively draining it out) > > so we can safely lift the nobackfill flag and let the cluster settle > > without hitting capacity limits. > > > > *My Questions for the Community:* > > > > What is the standard best practice for handling this "small bucket" > > transient imbalance when adding a small number of OSDs to a new host? Or > is > > this just a bad idea in general ? > > > > Is there a way to force the built-in upmap balancer to respect the > > transient/acting capacity of an OSD so it doesn't allow a drive to go > > towards 85% during a migration? I understand we were not there, but being > > 12 % away was "close" enough. > > > > One of the ideas was to reweight the offending OSD, to remove a few PGs, > so > > it would not be so close to nearfull situation. But this approach is > > tedious and requires "baby-sitting". > > > > I guess this might be a good candidate for upmap remap script, but we > were > > not "brave" enough to run in it a production environment the first time. > > > > Thanks, > > > > Robert > > _______________________________________________ > > ceph-users mailing list -- ceph-users(a)ceph.io > > To unsubscribe send an email to ceph-users-leave(a)ceph.io > > > _______________________________________________ > ceph-users mailing list -- ceph-users(a)ceph.io > To unsubscribe send an email to ceph-users-leave(a)ceph.io >

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New download.ceph.com package/repo signing key
by Dan Mick 04 Jul '26

04 Jul '26

Hi all. Recent releases (el10 in particular) started to complain about a SHA-1 algorithm in use for our release key (https://download.ceph.com/keys/release.asc) I have re-signed the portion of the key that was using the obsolete algorithm and the new key is available at the same location. You can tell the new key because it's 1660 bytes, and it has no "Version:" string in the text. Also, it will cleanly import into el10 rpm, whereas the original does not. This will fix el10 rpm's failure to verify the signature on .rpm files: error: Verifying a signature using certificate 08B73419AC32B4E966C1A330E84AC2C0460F3994 (Ceph.com (release key) <security(a)ceph.com>): 1. Certificate E84AC2C0460F3994 invalid: policy violation because: No binding signature at time 2025-10-03T17:18:24Z If you experience such errors, download the new key from https://tracker.ceph.com/issues/74861 and use rpm --import to store it in rpm's keyring. Details are in https://tracker.ceph.com/issues/74861. Feel free to email with questions. tl;dr: update your release.asc Ceph package-signing key.

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Re: CephFS large amounts of dark data
by Alex Gorbachev 03 Jul '26

03 Jul '26

I don't deal with CephFS much, but on RBD I had an issue like that, and it was because the filesystem needed fstrim. -- Alex Gorbachev ISS/Storcium On Fri, Jul 3, 2026 at 3:48 AM Andrej Filipčič via ceph-users < ceph-users(a)ceph.io> wrote: > On 3. 7. 2026 02:05, Anthony D'Atri via ceph-users wrote: > > A couple of ideas: > > > > Do you have osd_recovery_sleep_* set? > > osd_recovery_sleep_hdd 0.100000 > > osd_delete_sleep_*? > not that one > > Do you have any pools in the middle of pg_num adjustments, such that > pg_num != pgp_num and a pg_num_target is reported? > no, that one is fine, we have autoscaling disabled. > > Best, > Andrej > > > >> On Jul 2, 2026, at 2:52 PM, Andras Pataki via ceph-users < > ceph-users(a)ceph.io> wrote: > >> > >> Hi, > >> > >> I have also seen this on a recent large scale/parallel test I can on a > test setup. After creating about a hundred million files, then removing > all of them - there were thousands of objects left in the cephfs data pool > corresponding to inodes that no longer existed. I.e. it looks like the MDS > is "leaking" data - does not correctly delete all objects corresponding to > files in the purge queue. We have never used any snapshots on this file > system, so it definitely isn't about snapshots holding data. Also, we > increased the purge queue settings (filer_max_purge_ops, mds_max_purge_* > and friends) and definitely waited long enough for all deletes to be > processed (the objects were there weeks after the file system was emptied). > This was on a squid 19.2.3 cluster. > >> In the tests that lead to this, both the file creation and deletions > were done in parallel using a few dozen clients - stressing the MDS for > sure. We had no crashes/problems on the cluster, we never had to do any > data recovery steps, i.e. the MDS appeared to work fine through the tests. > Also, this was a single MDS cluster, i.e. the problem isn't related to > subtrees moving across MDS's for example. The problem became obvious since > after removing all data from cephfs, we were expecting the data pools to be > empty, but they weren't. There were two pools, a primary triple replicated > one and an erasure coded one. Both of them had stray objects. > >> > >> I didn't pursue this further since I wasn't sure what useful > information I could gather for a bug report - but it is certainly a curious > observation that perhaps large, long living cephfs clusters might have > significant space tied up in these objects that should have been removed > but weren't. Short of a full scan of all objects and matching them to > inodes - it is hard to tell how much even. > >> > >> Andras > >> > >> > >>> On 7/2/26 12:17 PM, Andrej Filipčič via ceph-users wrote: > >>> > >>> So, to follow up on this, I did some further investigation. > >>> > >>> Checking for write amplification, I have copied 250TB of a mix of > small and large files (20M of them), and the stored space on EC pool > matched what was expected from actual data size to a few %. So EC overhead > was not really a factor. Also, after the removal of this data set, the > stored space was recovered as expected. > >>> > >>> The I checked the full dump of cephfs and compared it to list of all > objects in the EC pool as follows: > >>> > >>> rados -p cephfs_data_echdd ls > echdd.objectlist > >>> > >>> find /ceph/ -printf "%i %p\n" > cephfs.inodes > >>> > >>> this took several hours, while in the meantime, writing and removing > of data to cephfs was relatively low (few MB/s), so the impact of new > objects and files should have been minimal. > >>> > >>> Then I selected all the objects of the form > >>> 1007b28abae.00000000 > >>> 100cce97f6d.00000000 > >>> 10067733861.00000000 > >>> 100cc4646aa.00000000 > >>> 200044d5c07.00000000 > >>> ... > >>> > >>> and checked if they match the files in the cephfs.inodes list > >>> > >>> ~3M of *.00000000 objects do not have the corresponding inode in the > cephfs.inodes > >>> > >>> > >>> I did "rados stat" of ~70k of these objects (still running for all of > them), and almost all have timestamps from March and April these year. On > 4th of May I remember I have increased the mds purge queue values to speed > up the removal of files since OSDs were filling up too quickly, and since > then it seems the objects are not left uncleaned any more. > >>> > >>> With "rados getxattr objectid parent" I have checked several of them, > and they all belong to two very active projects which typically write files > with few GB/s all the time (and remove as well so space usage is not > increasing). The objects I have checked belonged to files that were > removed in cephfs, the projects have a separate file catalog which is > consistent with cephfs contents. > >>> > >>> So, I do not understand why so many objects were left unremoved in EC > pool in the period of 2 months, but at least, 3M uncleaned files explains > 1.5PB of dark data by quick estimate. > >>> > >>> We also scrubbed cephfs root and ~mdsdir several times and no > leftovers to remove were found. > >>> > >>> I hope the problem is gone now, but I would still like a good advice > on how to proceed with the cleanup. I see these options: > >>> > >>> 1) remove the unmatched objects directly from EC pool with "rados > rm". But this might have undesired side effects or corruption. > >>> > >>> 2) create a new EC pool and migrate all the data there by copying > files in filesystem, and then destroy the old pool. > >>> > >>> 3) create a new filesystem with new EC pools and migrate the files. > >>> > >>> 4) run some advanced MDS disaster recovery procedure > (cephfs-data-scan), but this requires offline FS and I do not want to > recover old files from existing unmatched objects. Anyway, cephfs seems to > be healthy now. > >>> > >>> Any good ideas? > >>> > >>> Best, > >>> Andrej > >>> > >>> > >>> On 10. 6. 2026 01:36, Anthony D'Atri via ceph-users wrote: > >>>>> ). > >>>>>>> There is ~5.6PiB stored on /ceph, shown by ceph.dir.rbytes with > 132M files and 139M rentries. The pool shows 7PiB stored and 9.7PiB used > consistent with 8+3 EC. > >>>>>>> The layout for most files: > >>>>>>> ceph.dir.layout="stripe_unit=16777216 stripe_count=1 > object_size=16777216 pool=cephfs_data_echdd" > >>>>>>> > >>>>>>> But there is 1.4PiB discrepancy between the pool and the filesystem > >>>> Do you have scrubs enabled? Which if any non-default config options > do you have set? Any undersized or degraded or backfilling PGs? > >>>> > >>>> Which Ceph release? Do you have a sizable fraction of small files? > If you’re running Squid or earlier or don’t have EC optimizations enabled, > even a tiny file will allocate a multiple of 11*16=176 KB. An 129KB file > will consume 352KB, etc. If I understand those layout options correctly. > >>>> > >>>> If that’s what’s going on, going to Tentacle with EC optimizations > would gain you some efficiency for files newly [re]written. You could also > migrate small files to a replicated pool. > >>>> > >>>> > >>>>>>> which I cannot explain and I suspect there are a lot of orphan > objects there. I have run mds scrub on / and ~mdsdir as well. There is some > mds damage on some old small files (~400 files), which I do not think it's > relevant here. > >>>>>>> > >>>>>> Hello, > >>>>>> We had a similar issue last year with a group of users that created > and removed files at a very high rate. > >>>>>> > >>>>>> Have you read > https://urldefense.com/v3/__https://docs.clyso.com/docs/kb/cephfs/*cephfs-p… > ? > >>>>>> > >>>>>> We increased the purge rate parameters (very) aggressively to get > back to a comfortable situation (i.e. not a pool w/ near full warnings). > >>>>>> > >>>>>> > >>>>>> Loïc. > >>>>> -- > >>>>> _____________________________________________________________ > >>>>> prof. dr. Andrej Filipcic, E-mail: Andrej.Filipcic(a)ijs.si > >>>>> Department of Experimental High Energy Physics - F9 > >>>>> Jozef Stefan Institute, Jamova 39, P.o.Box 3000 > >>>>> SI-1001 Ljubljana, Slovenia > >>>>> Tel.: +386-1-477-3674 Fax: +386-1-477-3166 > >>>>> ------------------------------------------------------------- > >>>>> _______________________________________________ > >>>>> ceph-users mailing list -- ceph-users(a)ceph.io > >>>>> To unsubscribe send an email to ceph-users-leave(a)ceph.io > >>>> _______________________________________________ > >>>> ceph-users mailing list -- ceph-users(a)ceph.io > >>>> To unsubscribe send an email to ceph-users-leave(a)ceph.io > >>> > >> _______________________________________________ > >> ceph-users mailing list -- ceph-users(a)ceph.io > >> To unsubscribe send an email to ceph-users-leave(a)ceph.io > > _______________________________________________ > > ceph-users mailing list -- ceph-users(a)ceph.io > > To unsubscribe send an email to ceph-users-leave(a)ceph.io > > > -- > _____________________________________________________________ > prof. dr. Andrej Filipcic, E-mail: Andrej.Filipcic(a)ijs.si > Department of Experimental High Energy Physics - F9 > Jozef Stefan Institute, Jamova 39, P.o.Box 3000 > SI-1001 Ljubljana, Slovenia > Tel.: +386-1-477-3674 Fax: +386-1-477-3166 > ------------------------------------------------------------- > _______________________________________________ > ceph-users mailing list -- ceph-users(a)ceph.io > To unsubscribe send an email to ceph-users-leave(a)ceph.io >

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Re: Grafana dashboards warnings after upgrade to Squid 19.2.4
by Anthony D'Atri 03 Jul '26

03 Jul '26

[ I've left off dev@ from this reply, as it doesn't seem necessarily like a dev issue ] Is it possible that your cluster is overriding the default container images, assuming that you're running containerized with cephadm? root@squid1:~# ceph config dump | grep container_image container_image XX mgr/cephadm/container_image_alertmanager YY mgr/cephadm/container_image_base ZZ mgr/cephadm/container_image_elasticsearch QQ mgr/cephadm/container_image_grafana .. mgr/cephadm/container_image_haproxy .. mgr/cephadm/container_image_jaeger_agent .. mgr/cephadm/container_image_jaeger_collector .. mgr/cephadm/container_image_jaeger_query .. mgr/cephadm/container_image_keepalived .. mgr/cephadm/container_image_loki .. mgr/cephadm/container_image_node_exporter .. mgr/cephadm/container_image_nvmeof .. mgr/cephadm/container_image_prometheus .. mgr/cephadm/container_image_promtail .. mgr/cephadm/container_image_samba .. mgr/cephadm/container_image_snmp_gateway .. > On Jul 1, 2026, at 6:53 AM, Sake via ceph-users <ceph-users(a)ceph.io> wrote: > > Probably something not going correctly, because I just upgraded to 19.2.4 and Grafana is using the grafana image (in the past this was ceph-grafana) version 12.3.1. > > > On 1 July 2026 11:13:02 CEST, Eugen Block via ceph-users <ceph-users(a)ceph.io> wrote: >> Hi, >> >> I just upgraded our production cluster to 19.2.4 (from 19.2.3), there were no issues reported by our users, so all good. But I noticed that many graphs now show different warnings or strange labels: >> >> - "This panel requires Angular (deprecated)." on multiple graphs >> - "PromQL info: metric might not be a counter, name does not end in _total/_sum/_count/_bucket: "ceph_pool_wr" (1:6)" also on multiple graphs for different metrics >> - "OSD Capacity Utilization" just shows: "RangeError: invalid array length" >> - The "Pool Overview" graph has column names like "Value #F", "Value #G" and so on. And the values within don't make sense either. >> >> I have uploaded screenshots: >> >> https://www.pasteboard.co/A34Zcy9cqHe5.png >> https://www.pasteboard.co/F_vkpeBjGGWH.png >> https://www.pasteboard.co/mkCtlBN3zS6v.png >> https://www.pasteboard.co/T_ByD_gCpslA.png >> >> I compared the prometheus and grafana versions we have currently running with a fresh 19.2.4 bootstrapped cluster and the versions are identical: >> >> ceph orch ps --daemon-type grafana --format json | jq -r '.[].version' >> 10.4.0 >> >> ceph orch ps --daemon-type prometheus --format json | jq -r '.[].version' >> 2.51.0 >> >> Is there anything I'm missing? >> >> Thanks! >> Eugen >> _______________________________________________ >> ceph-users mailing list -- ceph-users(a)ceph.io >> To unsubscribe send an email to ceph-users-leave(a)ceph.io > _______________________________________________ > ceph-users mailing list -- ceph-users(a)ceph.io > To unsubscribe send an email to ceph-users-leave(a)ceph.io

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Re: CephFS large amounts of dark data
by Andrej Filipčič 03 Jul '26

03 Jul '26

On 3. 7. 2026 02:05, Anthony D'Atri via ceph-users wrote: > A couple of ideas: > > Do you have osd_recovery_sleep_* set? osd_recovery_sleep_hdd 0.100000 > osd_delete_sleep_*? not that one > Do you have any pools in the middle of pg_num adjustments, such that pg_num != pgp_num and a pg_num_target is reported? no, that one is fine, we have autoscaling disabled. Best, Andrej > >> On Jul 2, 2026, at 2:52 PM, Andras Pataki via ceph-users <ceph-users(a)ceph.io> wrote: >> >> Hi, >> >> I have also seen this on a recent large scale/parallel test I can on a test setup. After creating about a hundred million files, then removing all of them - there were thousands of objects left in the cephfs data pool corresponding to inodes that no longer existed. I.e. it looks like the MDS is "leaking" data - does not correctly delete all objects corresponding to files in the purge queue. We have never used any snapshots on this file system, so it definitely isn't about snapshots holding data. Also, we increased the purge queue settings (filer_max_purge_ops, mds_max_purge_* and friends) and definitely waited long enough for all deletes to be processed (the objects were there weeks after the file system was emptied). This was on a squid 19.2.3 cluster. >> In the tests that lead to this, both the file creation and deletions were done in parallel using a few dozen clients - stressing the MDS for sure. We had no crashes/problems on the cluster, we never had to do any data recovery steps, i.e. the MDS appeared to work fine through the tests. Also, this was a single MDS cluster, i.e. the problem isn't related to subtrees moving across MDS's for example. The problem became obvious since after removing all data from cephfs, we were expecting the data pools to be empty, but they weren't. There were two pools, a primary triple replicated one and an erasure coded one. Both of them had stray objects. >> >> I didn't pursue this further since I wasn't sure what useful information I could gather for a bug report - but it is certainly a curious observation that perhaps large, long living cephfs clusters might have significant space tied up in these objects that should have been removed but weren't. Short of a full scan of all objects and matching them to inodes - it is hard to tell how much even. >> >> Andras >> >> >>> On 7/2/26 12:17 PM, Andrej Filipčič via ceph-users wrote: >>> >>> So, to follow up on this, I did some further investigation. >>> >>> Checking for write amplification, I have copied 250TB of a mix of small and large files (20M of them), and the stored space on EC pool matched what was expected from actual data size to a few %. So EC overhead was not really a factor. Also, after the removal of this data set, the stored space was recovered as expected. >>> >>> The I checked the full dump of cephfs and compared it to list of all objects in the EC pool as follows: >>> >>> rados -p cephfs_data_echdd ls > echdd.objectlist >>> >>> find /ceph/ -printf "%i %p\n" > cephfs.inodes >>> >>> this took several hours, while in the meantime, writing and removing of data to cephfs was relatively low (few MB/s), so the impact of new objects and files should have been minimal. >>> >>> Then I selected all the objects of the form >>> 1007b28abae.00000000 >>> 100cce97f6d.00000000 >>> 10067733861.00000000 >>> 100cc4646aa.00000000 >>> 200044d5c07.00000000 >>> ... >>> >>> and checked if they match the files in the cephfs.inodes list >>> >>> ~3M of *.00000000 objects do not have the corresponding inode in the cephfs.inodes >>> >>> >>> I did "rados stat" of ~70k of these objects (still running for all of them), and almost all have timestamps from March and April these year. On 4th of May I remember I have increased the mds purge queue values to speed up the removal of files since OSDs were filling up too quickly, and since then it seems the objects are not left uncleaned any more. >>> >>> With "rados getxattr objectid parent" I have checked several of them, and they all belong to two very active projects which typically write files with few GB/s all the time (and remove as well so space usage is not increasing). The objects I have checked belonged to files that were removed in cephfs, the projects have a separate file catalog which is consistent with cephfs contents. >>> >>> So, I do not understand why so many objects were left unremoved in EC pool in the period of 2 months, but at least, 3M uncleaned files explains 1.5PB of dark data by quick estimate. >>> >>> We also scrubbed cephfs root and ~mdsdir several times and no leftovers to remove were found. >>> >>> I hope the problem is gone now, but I would still like a good advice on how to proceed with the cleanup. I see these options: >>> >>> 1) remove the unmatched objects directly from EC pool with "rados rm". But this might have undesired side effects or corruption. >>> >>> 2) create a new EC pool and migrate all the data there by copying files in filesystem, and then destroy the old pool. >>> >>> 3) create a new filesystem with new EC pools and migrate the files. >>> >>> 4) run some advanced MDS disaster recovery procedure (cephfs-data-scan), but this requires offline FS and I do not want to recover old files from existing unmatched objects. Anyway, cephfs seems to be healthy now. >>> >>> Any good ideas? >>> >>> Best, >>> Andrej >>> >>> >>> On 10. 6. 2026 01:36, Anthony D'Atri via ceph-users wrote: >>>>> ). >>>>>>> There is ~5.6PiB stored on /ceph, shown by ceph.dir.rbytes with 132M files and 139M rentries. The pool shows 7PiB stored and 9.7PiB used consistent with 8+3 EC. >>>>>>> The layout for most files: >>>>>>> ceph.dir.layout="stripe_unit=16777216 stripe_count=1 object_size=16777216 pool=cephfs_data_echdd" >>>>>>> >>>>>>> But there is 1.4PiB discrepancy between the pool and the filesystem >>>> Do you have scrubs enabled? Which if any non-default config options do you have set? Any undersized or degraded or backfilling PGs? >>>> >>>> Which Ceph release? Do you have a sizable fraction of small files? If you’re running Squid or earlier or don’t have EC optimizations enabled, even a tiny file will allocate a multiple of 11*16=176 KB. An 129KB file will consume 352KB, etc. If I understand those layout options correctly. >>>> >>>> If that’s what’s going on, going to Tentacle with EC optimizations would gain you some efficiency for files newly [re]written. You could also migrate small files to a replicated pool. >>>> >>>> >>>>>>> which I cannot explain and I suspect there are a lot of orphan objects there. I have run mds scrub on / and ~mdsdir as well. There is some mds damage on some old small files (~400 files), which I do not think it's relevant here. >>>>>>> >>>>>> Hello, >>>>>> We had a similar issue last year with a group of users that created and removed files at a very high rate. >>>>>> >>>>>> Have you read https://urldefense.com/v3/__https://docs.clyso.com/docs/kb/cephfs/*cephfs-p… ? >>>>>> >>>>>> We increased the purge rate parameters (very) aggressively to get back to a comfortable situation (i.e. not a pool w/ near full warnings). >>>>>> >>>>>> >>>>>> Loïc. >>>>> -- >>>>> _____________________________________________________________ >>>>> prof. dr. Andrej Filipcic, E-mail: Andrej.Filipcic(a)ijs.si >>>>> Department of Experimental High Energy Physics - F9 >>>>> Jozef Stefan Institute, Jamova 39, P.o.Box 3000 >>>>> SI-1001 Ljubljana, Slovenia >>>>> Tel.: +386-1-477-3674 Fax: +386-1-477-3166 >>>>> ------------------------------------------------------------- >>>>> _______________________________________________ >>>>> ceph-users mailing list -- ceph-users(a)ceph.io >>>>> To unsubscribe send an email to ceph-users-leave(a)ceph.io >>>> _______________________________________________ >>>> ceph-users mailing list -- ceph-users(a)ceph.io >>>> To unsubscribe send an email to ceph-users-leave(a)ceph.io >>> >> _______________________________________________ >> ceph-users mailing list -- ceph-users(a)ceph.io >> To unsubscribe send an email to ceph-users-leave(a)ceph.io > _______________________________________________ > ceph-users mailing list -- ceph-users(a)ceph.io > To unsubscribe send an email to ceph-users-leave(a)ceph.io -- _____________________________________________________________ prof. dr. Andrej Filipcic, E-mail: Andrej.Filipcic(a)ijs.si Department of Experimental High Energy Physics - F9 Jozef Stefan Institute, Jamova 39, P.o.Box 3000 SI-1001 Ljubljana, Slovenia Tel.: +386-1-477-3674 Fax: +386-1-477-3166 -------------------------------------------------------------

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Re: CephFS large amounts of dark data
by Gregory Farnum 03 Jul '26

03 Jul '26

Hmm, this is unfortunate news. I don’t think I’ve heard about anything like this before. Andrej, what Ceph version are you running, and has it changed during this time frame? I would imagine the most likely thing to be our “purge queue” is somehow some times not deleting objects that it marks as removed. But I’ve no idea how that could go wrong. As much information as we can get about stuff like mds restarts during the deletion, single or mult-mds, precise versions, and any pool or file layouts may help narrow things down. (For instance, it may be that the leak only happens if using multiple data pools, or if it was written on a particular version and a later buggy version parses something wrong.) -Greg On Thu, Jul 2, 2026 at 8:53 AM Andras Pataki via ceph-users < ceph-users(a)ceph.io> wrote: > Hi, > > I have also seen this on a recent large scale/parallel test I can on a > test setup. After creating about a hundred million files, then removing > all of them - there were thousands of objects left in the cephfs data > pool corresponding to inodes that no longer existed. I.e. it looks like > the MDS is "leaking" data - does not correctly delete all objects > corresponding to files in the purge queue. We have never used any > snapshots on this file system, so it definitely isn't about snapshots > holding data. Also, we increased the purge queue settings > (filer_max_purge_ops, mds_max_purge_* and friends) and definitely waited > long enough for all deletes to be processed (the objects were there > weeks after the file system was emptied). This was on a squid 19.2.3 > cluster. > In the tests that lead to this, both the file creation and deletions > were done in parallel using a few dozen clients - stressing the MDS for > sure. We had no crashes/problems on the cluster, we never had to do any > data recovery steps, i.e. the MDS appeared to work fine through the > tests. Also, this was a single MDS cluster, i.e. the problem isn't > related to subtrees moving across MDS's for example. The problem became > obvious since after removing all data from cephfs, we were expecting the > data pools to be empty, but they weren't. There were two pools, a > primary triple replicated one and an erasure coded one. Both of them > had stray objects. > > I didn't pursue this further since I wasn't sure what useful information > I could gather for a bug report - but it is certainly a curious > observation that perhaps large, long living cephfs clusters might have > significant space tied up in these objects that should have been removed > but weren't. Short of a full scan of all objects and matching them to > inodes - it is hard to tell how much even. > > Andras > > > On 7/2/26 12:17 PM, Andrej Filipčič via ceph-users wrote: > > > > So, to follow up on this, I did some further investigation. > > > > Checking for write amplification, I have copied 250TB of a mix of > > small and large files (20M of them), and the stored space on EC pool > > matched what was expected from actual data size to a few %. So EC > > overhead was not really a factor. Also, after the removal of this data > > set, the stored space was recovered as expected. > > > > The I checked the full dump of cephfs and compared it to list of all > > objects in the EC pool as follows: > > > > rados -p cephfs_data_echdd ls > echdd.objectlist > > > > find /ceph/ -printf "%i %p\n" > cephfs.inodes > > > > this took several hours, while in the meantime, writing and removing > > of data to cephfs was relatively low (few MB/s), so the impact of new > > objects and files should have been minimal. > > > > Then I selected all the objects of the form > > 1007b28abae.00000000 > > 100cce97f6d.00000000 > > 10067733861.00000000 > > 100cc4646aa.00000000 > > 200044d5c07.00000000 > > ... > > > > and checked if they match the files in the cephfs.inodes list > > > > ~3M of *.00000000 objects do not have the corresponding inode in the > > cephfs.inodes > > > > > > I did "rados stat" of ~70k of these objects (still running for all of > > them), and almost all have timestamps from March and April these year. > > On 4th of May I remember I have increased the mds purge queue values > > to speed up the removal of files since OSDs were filling up too > > quickly, and since then it seems the objects are not left uncleaned > > any more. > > > > With "rados getxattr objectid parent" I have checked several of them, > > and they all belong to two very active projects which typically write > > files with few GB/s all the time (and remove as well so space usage is > > not increasing). The objects I have checked belonged to files that > > were removed in cephfs, the projects have a separate file catalog > > which is consistent with cephfs contents. > > > > So, I do not understand why so many objects were left unremoved in EC > > pool in the period of 2 months, but at least, 3M uncleaned files > > explains 1.5PB of dark data by quick estimate. > > > > We also scrubbed cephfs root and ~mdsdir several times and no > > leftovers to remove were found. > > > > I hope the problem is gone now, but I would still like a good advice > > on how to proceed with the cleanup. I see these options: > > > > 1) remove the unmatched objects directly from EC pool with "rados > > rm". But this might have undesired side effects or corruption. > > > > 2) create a new EC pool and migrate all the data there by copying > > files in filesystem, and then destroy the old pool. > > > > 3) create a new filesystem with new EC pools and migrate the files. > > > > 4) run some advanced MDS disaster recovery procedure > > (cephfs-data-scan), but this requires offline FS and I do not want to > > recover old files from existing unmatched objects. Anyway, cephfs > > seems to be healthy now. > > > > Any good ideas? > > > > Best, > > Andrej > > > > > > On 10. 6. 2026 01:36, Anthony D'Atri via ceph-users wrote: > >>> ). > >>>>> There is ~5.6PiB stored on /ceph, shown by ceph.dir.rbytes with > >>>>> 132M files and 139M rentries. The pool shows 7PiB stored and > >>>>> 9.7PiB used consistent with 8+3 EC. > >>>>> The layout for most files: > >>>>> ceph.dir.layout="stripe_unit=16777216 stripe_count=1 > >>>>> object_size=16777216 pool=cephfs_data_echdd" > >>>>> > >>>>> But there is 1.4PiB discrepancy between the pool and the filesystem > >> Do you have scrubs enabled? Which if any non-default config options > >> do you have set? Any undersized or degraded or backfilling PGs? > >> > >> Which Ceph release? Do you have a sizable fraction of small files? > >> If you’re running Squid or earlier or don’t have EC optimizations > >> enabled, even a tiny file will allocate a multiple of 11*16=176 KB. > >> An 129KB file will consume 352KB, etc. If I understand those layout > >> options correctly. > >> > >> If that’s what’s going on, going to Tentacle with EC optimizations > >> would gain you some efficiency for files newly [re]written. You > >> could also migrate small files to a replicated pool. > >> > >> > >>>>> which I cannot explain and I suspect there are a lot of orphan > >>>>> objects there. I have run mds scrub on / and ~mdsdir as well. > >>>>> There is some mds damage on some old small files (~400 files), > >>>>> which I do not think it's relevant here. > >>>>> > >>>> Hello, > >>>> We had a similar issue last year with a group of users that created > >>>> and removed files at a very high rate. > >>>> > >>>> Have you read > >>>> > https://urldefense.com/v3/__https://docs.clyso.com/docs/kb/cephfs/*cephfs-p… > >>>> ? > >>>> > >>>> We increased the purge rate parameters (very) aggressively to get > >>>> back to a comfortable situation (i.e. not a pool w/ near full > >>>> warnings). > >>>> > >>>> > >>>> Loïc. > >>> > >>> -- > >>> _____________________________________________________________ > >>> prof. dr. Andrej Filipcic, E-mail: Andrej.Filipcic(a)ijs.si > >>> Department of Experimental High Energy Physics - F9 > >>> Jozef Stefan Institute, Jamova 39, P.o.Box 3000 > >>> SI-1001 Ljubljana, Slovenia > >>> Tel.: +386-1-477-3674 Fax: +386-1-477-3166 > >>> ------------------------------------------------------------- > >>> _______________________________________________ > >>> ceph-users mailing list -- ceph-users(a)ceph.io > >>> To unsubscribe send an email to ceph-users-leave(a)ceph.io > >> _______________________________________________ > >> ceph-users mailing list -- ceph-users(a)ceph.io > >> To unsubscribe send an email to ceph-users-leave(a)ceph.io > > > > > _______________________________________________ > ceph-users mailing list -- ceph-users(a)ceph.io > To unsubscribe send an email to ceph-users-leave(a)ceph.io > >

2 1

Re: CephFS large amounts of dark data
by Anthony D'Atri 03 Jul '26

03 Jul '26

A couple of ideas: Do you have osd_recovery_sleep_* set? osd_delete_sleep_*? Do you have any pools in the middle of pg_num adjustments, such that pg_num != pgp_num and a pg_num_target is reported? > On Jul 2, 2026, at 2:52 PM, Andras Pataki via ceph-users <ceph-users(a)ceph.io> wrote: > > Hi, > > I have also seen this on a recent large scale/parallel test I can on a test setup. After creating about a hundred million files, then removing all of them - there were thousands of objects left in the cephfs data pool corresponding to inodes that no longer existed. I.e. it looks like the MDS is "leaking" data - does not correctly delete all objects corresponding to files in the purge queue. We have never used any snapshots on this file system, so it definitely isn't about snapshots holding data. Also, we increased the purge queue settings (filer_max_purge_ops, mds_max_purge_* and friends) and definitely waited long enough for all deletes to be processed (the objects were there weeks after the file system was emptied). This was on a squid 19.2.3 cluster. > In the tests that lead to this, both the file creation and deletions were done in parallel using a few dozen clients - stressing the MDS for sure. We had no crashes/problems on the cluster, we never had to do any data recovery steps, i.e. the MDS appeared to work fine through the tests. Also, this was a single MDS cluster, i.e. the problem isn't related to subtrees moving across MDS's for example. The problem became obvious since after removing all data from cephfs, we were expecting the data pools to be empty, but they weren't. There were two pools, a primary triple replicated one and an erasure coded one. Both of them had stray objects. > > I didn't pursue this further since I wasn't sure what useful information I could gather for a bug report - but it is certainly a curious observation that perhaps large, long living cephfs clusters might have significant space tied up in these objects that should have been removed but weren't. Short of a full scan of all objects and matching them to inodes - it is hard to tell how much even. > > Andras > > >> On 7/2/26 12:17 PM, Andrej Filipčič via ceph-users wrote: >> >> So, to follow up on this, I did some further investigation. >> >> Checking for write amplification, I have copied 250TB of a mix of small and large files (20M of them), and the stored space on EC pool matched what was expected from actual data size to a few %. So EC overhead was not really a factor. Also, after the removal of this data set, the stored space was recovered as expected. >> >> The I checked the full dump of cephfs and compared it to list of all objects in the EC pool as follows: >> >> rados -p cephfs_data_echdd ls > echdd.objectlist >> >> find /ceph/ -printf "%i %p\n" > cephfs.inodes >> >> this took several hours, while in the meantime, writing and removing of data to cephfs was relatively low (few MB/s), so the impact of new objects and files should have been minimal. >> >> Then I selected all the objects of the form >> 1007b28abae.00000000 >> 100cce97f6d.00000000 >> 10067733861.00000000 >> 100cc4646aa.00000000 >> 200044d5c07.00000000 >> ... >> >> and checked if they match the files in the cephfs.inodes list >> >> ~3M of *.00000000 objects do not have the corresponding inode in the cephfs.inodes >> >> >> I did "rados stat" of ~70k of these objects (still running for all of them), and almost all have timestamps from March and April these year. On 4th of May I remember I have increased the mds purge queue values to speed up the removal of files since OSDs were filling up too quickly, and since then it seems the objects are not left uncleaned any more. >> >> With "rados getxattr objectid parent" I have checked several of them, and they all belong to two very active projects which typically write files with few GB/s all the time (and remove as well so space usage is not increasing). The objects I have checked belonged to files that were removed in cephfs, the projects have a separate file catalog which is consistent with cephfs contents. >> >> So, I do not understand why so many objects were left unremoved in EC pool in the period of 2 months, but at least, 3M uncleaned files explains 1.5PB of dark data by quick estimate. >> >> We also scrubbed cephfs root and ~mdsdir several times and no leftovers to remove were found. >> >> I hope the problem is gone now, but I would still like a good advice on how to proceed with the cleanup. I see these options: >> >> 1) remove the unmatched objects directly from EC pool with "rados rm". But this might have undesired side effects or corruption. >> >> 2) create a new EC pool and migrate all the data there by copying files in filesystem, and then destroy the old pool. >> >> 3) create a new filesystem with new EC pools and migrate the files. >> >> 4) run some advanced MDS disaster recovery procedure (cephfs-data-scan), but this requires offline FS and I do not want to recover old files from existing unmatched objects. Anyway, cephfs seems to be healthy now. >> >> Any good ideas? >> >> Best, >> Andrej >> >> >> On 10. 6. 2026 01:36, Anthony D'Atri via ceph-users wrote: >>>> ). >>>>>> There is ~5.6PiB stored on /ceph, shown by ceph.dir.rbytes with 132M files and 139M rentries. The pool shows 7PiB stored and 9.7PiB used consistent with 8+3 EC. >>>>>> The layout for most files: >>>>>> ceph.dir.layout="stripe_unit=16777216 stripe_count=1 object_size=16777216 pool=cephfs_data_echdd" >>>>>> >>>>>> But there is 1.4PiB discrepancy between the pool and the filesystem >>> Do you have scrubs enabled? Which if any non-default config options do you have set? Any undersized or degraded or backfilling PGs? >>> >>> Which Ceph release? Do you have a sizable fraction of small files? If you’re running Squid or earlier or don’t have EC optimizations enabled, even a tiny file will allocate a multiple of 11*16=176 KB. An 129KB file will consume 352KB, etc. If I understand those layout options correctly. >>> >>> If that’s what’s going on, going to Tentacle with EC optimizations would gain you some efficiency for files newly [re]written. You could also migrate small files to a replicated pool. >>> >>> >>>>>> which I cannot explain and I suspect there are a lot of orphan objects there. I have run mds scrub on / and ~mdsdir as well. There is some mds damage on some old small files (~400 files), which I do not think it's relevant here. >>>>>> >>>>> Hello, >>>>> We had a similar issue last year with a group of users that created and removed files at a very high rate. >>>>> >>>>> Have you read https://urldefense.com/v3/__https://docs.clyso.com/docs/kb/cephfs/*cephfs-p… ? >>>>> >>>>> We increased the purge rate parameters (very) aggressively to get back to a comfortable situation (i.e. not a pool w/ near full warnings). >>>>> >>>>> >>>>> Loïc. >>>> >>>> -- >>>> _____________________________________________________________ >>>> prof. dr. Andrej Filipcic, E-mail: Andrej.Filipcic(a)ijs.si >>>> Department of Experimental High Energy Physics - F9 >>>> Jozef Stefan Institute, Jamova 39, P.o.Box 3000 >>>> SI-1001 Ljubljana, Slovenia >>>> Tel.: +386-1-477-3674 Fax: +386-1-477-3166 >>>> ------------------------------------------------------------- >>>> _______________________________________________ >>>> ceph-users mailing list -- ceph-users(a)ceph.io >>>> To unsubscribe send an email to ceph-users-leave(a)ceph.io >>> _______________________________________________ >>> ceph-users mailing list -- ceph-users(a)ceph.io >>> To unsubscribe send an email to ceph-users-leave(a)ceph.io >> >> > _______________________________________________ > ceph-users mailing list -- ceph-users(a)ceph.io > To unsubscribe send an email to ceph-users-leave(a)ceph.io

1 0

Re: CephFS large amounts of dark data
by Andras Pataki 02 Jul '26

02 Jul '26

Hi, I have also seen this on a recent large scale/parallel test I can on a test setup. After creating about a hundred million files, then removing all of them - there were thousands of objects left in the cephfs data pool corresponding to inodes that no longer existed. I.e. it looks like the MDS is "leaking" data - does not correctly delete all objects corresponding to files in the purge queue. We have never used any snapshots on this file system, so it definitely isn't about snapshots holding data. Also, we increased the purge queue settings (filer_max_purge_ops, mds_max_purge_* and friends) and definitely waited long enough for all deletes to be processed (the objects were there weeks after the file system was emptied). This was on a squid 19.2.3 cluster. In the tests that lead to this, both the file creation and deletions were done in parallel using a few dozen clients - stressing the MDS for sure. We had no crashes/problems on the cluster, we never had to do any data recovery steps, i.e. the MDS appeared to work fine through the tests. Also, this was a single MDS cluster, i.e. the problem isn't related to subtrees moving across MDS's for example. The problem became obvious since after removing all data from cephfs, we were expecting the data pools to be empty, but they weren't. There were two pools, a primary triple replicated one and an erasure coded one. Both of them had stray objects. I didn't pursue this further since I wasn't sure what useful information I could gather for a bug report - but it is certainly a curious observation that perhaps large, long living cephfs clusters might have significant space tied up in these objects that should have been removed but weren't. Short of a full scan of all objects and matching them to inodes - it is hard to tell how much even. Andras On 7/2/26 12:17 PM, Andrej Filipčič via ceph-users wrote: > > So, to follow up on this, I did some further investigation. > > Checking for write amplification, I have copied 250TB of a mix of > small and large files (20M of them), and the stored space on EC pool > matched what was expected from actual data size to a few %. So EC > overhead was not really a factor. Also, after the removal of this data > set, the stored space was recovered as expected. > > The I checked the full dump of cephfs and compared it to list of all > objects in the EC pool as follows: > > rados -p cephfs_data_echdd ls > echdd.objectlist > > find /ceph/ -printf "%i %p\n" > cephfs.inodes > > this took several hours, while in the meantime, writing and removing > of data to cephfs was relatively low (few MB/s), so the impact of new > objects and files should have been minimal. > > Then I selected all the objects of the form > 1007b28abae.00000000 > 100cce97f6d.00000000 > 10067733861.00000000 > 100cc4646aa.00000000 > 200044d5c07.00000000 > ... > > and checked if they match the files in the cephfs.inodes list > > ~3M of *.00000000 objects do not have the corresponding inode in the > cephfs.inodes > > > I did "rados stat" of ~70k of these objects (still running for all of > them), and almost all have timestamps from March and April these year. > On 4th of May I remember I have increased the mds purge queue values > to speed up the removal of files since OSDs were filling up too > quickly, and since then it seems the objects are not left uncleaned > any more. > > With "rados getxattr objectid parent" I have checked several of them, > and they all belong to two very active projects which typically write > files with few GB/s all the time (and remove as well so space usage is > not increasing). The objects I have checked belonged to files that > were removed in cephfs, the projects have a separate file catalog > which is consistent with cephfs contents. > > So, I do not understand why so many objects were left unremoved in EC > pool in the period of 2 months, but at least, 3M uncleaned files > explains 1.5PB of dark data by quick estimate. > > We also scrubbed cephfs root and ~mdsdir several times and no > leftovers to remove were found. > > I hope the problem is gone now, but I would still like a good advice > on how to proceed with the cleanup. I see these options: > > 1) remove the unmatched objects directly from EC pool with "rados > rm". But this might have undesired side effects or corruption. > > 2) create a new EC pool and migrate all the data there by copying > files in filesystem, and then destroy the old pool. > > 3) create a new filesystem with new EC pools and migrate the files. > > 4) run some advanced MDS disaster recovery procedure > (cephfs-data-scan), but this requires offline FS and I do not want to > recover old files from existing unmatched objects. Anyway, cephfs > seems to be healthy now. > > Any good ideas? > > Best, > Andrej > > > On 10. 6. 2026 01:36, Anthony D'Atri via ceph-users wrote: >>> ). >>>>> There is ~5.6PiB stored on /ceph, shown by ceph.dir.rbytes with >>>>> 132M files and 139M rentries. The pool shows 7PiB stored and >>>>> 9.7PiB used consistent with 8+3 EC. >>>>> The layout for most files: >>>>> ceph.dir.layout="stripe_unit=16777216 stripe_count=1 >>>>> object_size=16777216 pool=cephfs_data_echdd" >>>>> >>>>> But there is 1.4PiB discrepancy between the pool and the filesystem >> Do you have scrubs enabled? Which if any non-default config options >> do you have set? Any undersized or degraded or backfilling PGs? >> >> Which Ceph release? Do you have a sizable fraction of small files? >> If you’re running Squid or earlier or don’t have EC optimizations >> enabled, even a tiny file will allocate a multiple of 11*16=176 KB. >> An 129KB file will consume 352KB, etc. If I understand those layout >> options correctly. >> >> If that’s what’s going on, going to Tentacle with EC optimizations >> would gain you some efficiency for files newly [re]written. You >> could also migrate small files to a replicated pool. >> >> >>>>> which I cannot explain and I suspect there are a lot of orphan >>>>> objects there. I have run mds scrub on / and ~mdsdir as well. >>>>> There is some mds damage on some old small files (~400 files), >>>>> which I do not think it's relevant here. >>>>> >>>> Hello, >>>> We had a similar issue last year with a group of users that created >>>> and removed files at a very high rate. >>>> >>>> Have you read >>>> https://urldefense.com/v3/__https://docs.clyso.com/docs/kb/cephfs/*cephfs-p… >>>> ? >>>> >>>> We increased the purge rate parameters (very) aggressively to get >>>> back to a comfortable situation (i.e. not a pool w/ near full >>>> warnings). >>>> >>>> >>>> Loïc. >>> >>> -- >>> _____________________________________________________________ >>> prof. dr. Andrej Filipcic, E-mail: Andrej.Filipcic(a)ijs.si >>> Department of Experimental High Energy Physics - F9 >>> Jozef Stefan Institute, Jamova 39, P.o.Box 3000 >>> SI-1001 Ljubljana, Slovenia >>> Tel.: +386-1-477-3674 Fax: +386-1-477-3166 >>> ------------------------------------------------------------- >>> _______________________________________________ >>> ceph-users mailing list -- ceph-users(a)ceph.io >>> To unsubscribe send an email to ceph-users-leave(a)ceph.io >> _______________________________________________ >> ceph-users mailing list -- ceph-users(a)ceph.io >> To unsubscribe send an email to ceph-users-leave(a)ceph.io > >

1 0

Re: CephFS large amounts of dark data
by Andrej Filipčič 02 Jul '26

02 Jul '26

So, to follow up on this, I did some further investigation. Checking for write amplification, I have copied 250TB of a mix of small and large files (20M of them), and the stored space on EC pool matched what was expected from actual data size to a few %. So EC overhead was not really a factor. Also, after the removal of this data set, the stored space was recovered as expected. The I checked the full dump of cephfs and compared it to list of all objects in the EC pool as follows: rados -p cephfs_data_echdd ls > echdd.objectlist find /ceph/ -printf "%i %p\n" > cephfs.inodes this took several hours, while in the meantime, writing and removing of data to cephfs was relatively low (few MB/s), so the impact of new objects and files should have been minimal. Then I selected all the objects of the form 1007b28abae.00000000 100cce97f6d.00000000 10067733861.00000000 100cc4646aa.00000000 200044d5c07.00000000 ... and checked if they match the files in the cephfs.inodes list ~3M of *.00000000 objects do not have the corresponding inode in the cephfs.inodes I did "rados stat" of ~70k of these objects (still running for all of them), and almost all have timestamps from March and April these year. On 4th of May I remember I have increased the mds purge queue values to speed up the removal of files since OSDs were filling up too quickly, and since then it seems the objects are not left uncleaned any more. With "rados getxattr objectid parent" I have checked several of them, and they all belong to two very active projects which typically write files with few GB/s all the time (and remove as well so space usage is not increasing). The objects I have checked belonged to files that were removed in cephfs, the projects have a separate file catalog which is consistent with cephfs contents. So, I do not understand why so many objects were left unremoved in EC pool in the period of 2 months, but at least, 3M uncleaned files explains 1.5PB of dark data by quick estimate. We also scrubbed cephfs root and ~mdsdir several times and no leftovers to remove were found. I hope the problem is gone now, but I would still like a good advice on how to proceed with the cleanup. I see these options: 1) remove the unmatched objects directly from EC pool with "rados rm". But this might have undesired side effects or corruption. 2) create a new EC pool and migrate all the data there by copying files in filesystem, and then destroy the old pool. 3) create a new filesystem with new EC pools and migrate the files. 4) run some advanced MDS disaster recovery procedure (cephfs-data-scan), but this requires offline FS and I do not want to recover old files from existing unmatched objects. Anyway, cephfs seems to be healthy now. Any good ideas? Best, Andrej On 10. 6. 2026 01:36, Anthony D'Atri via ceph-users wrote: >> ). >>>> There is ~5.6PiB stored on /ceph, shown by ceph.dir.rbytes with 132M files and 139M rentries. The pool shows 7PiB stored and 9.7PiB used consistent with 8+3 EC. >>>> The layout for most files: >>>> ceph.dir.layout="stripe_unit=16777216 stripe_count=1 object_size=16777216 pool=cephfs_data_echdd" >>>> >>>> But there is 1.4PiB discrepancy between the pool and the filesystem > Do you have scrubs enabled? Which if any non-default config options do you have set? Any undersized or degraded or backfilling PGs? > > Which Ceph release? Do you have a sizable fraction of small files? If you’re running Squid or earlier or don’t have EC optimizations enabled, even a tiny file will allocate a multiple of 11*16=176 KB. An 129KB file will consume 352KB, etc. If I understand those layout options correctly. > > If that’s what’s going on, going to Tentacle with EC optimizations would gain you some efficiency for files newly [re]written. You could also migrate small files to a replicated pool. > > >>>> which I cannot explain and I suspect there are a lot of orphan objects there. I have run mds scrub on / and ~mdsdir as well. There is some mds damage on some old small files (~400 files), which I do not think it's relevant here. >>>> >>> Hello, >>> We had a similar issue last year with a group of users that created and removed files at a very high rate. >>> >>> Have you read https://docs.clyso.com/docs/kb/cephfs/#cephfs-pool-data-usage-growth-withou… ? >>> >>> We increased the purge rate parameters (very) aggressively to get back to a comfortable situation (i.e. not a pool w/ near full warnings). >>> >>> >>> Loïc. >> >> -- >> _____________________________________________________________ >> prof. dr. Andrej Filipcic, E-mail: Andrej.Filipcic(a)ijs.si >> Department of Experimental High Energy Physics - F9 >> Jozef Stefan Institute, Jamova 39, P.o.Box 3000 >> SI-1001 Ljubljana, Slovenia >> Tel.: +386-1-477-3674 Fax: +386-1-477-3166 >> ------------------------------------------------------------- >> _______________________________________________ >> ceph-users mailing list -- ceph-users(a)ceph.io >> To unsubscribe send an email to ceph-users-leave(a)ceph.io > _______________________________________________ > ceph-users mailing list -- ceph-users(a)ceph.io > To unsubscribe send an email to ceph-users-leave(a)ceph.io -- _____________________________________________________________ prof. dr. Andrej Filipcic, E-mail: Andrej.Filipcic(a)ijs.si Department of Experimental High Energy Physics - F9 Jozef Stefan Institute, Jamova 39, P.o.Box 3000 SI-1001 Ljubljana, Slovenia Tel.: +386-1-477-3674 Fax: +386-1-477-3166 -------------------------------------------------------------

1 0

Re: An issue during expanding an cluster - one osd getting close to nearfull
by Anthony D'Atri 01 Jul '26

01 Jul '26

With 5x existing hosts and Proxmox, I suspect that Robert's cluster is using RBD with 3x replication and is okay in this respect. There were a couple of bugs wrt uneven failure domain weights back around Firefly, but not recently. Is it possible that any of your OSDs have old-style override reweights? The REWEIGHT column of `ceph osd tree` ? That can confuse a cluster using pg-upmap. Please follow up with a copy of `ceph osd df tree` Another approach is https://www.clyso.com/us/adding-capacity-to-ceph-the-clyso-way/ upmap-remapped -- be sure to have the latest version -- is a terrific tool. With this strategy you avoid the thundering herd of backfill, and since the balancer will only move a smaller bite at a time, you avoid the dynamic of intermediate states filling up OSDs. A certain Ceph installation added 40 hosts (yes, you read that right) at once to a cluster and ran into this, though with a smaller upgrade I wouldn't expect to see the problem. With this approach most or all of the backfill gets cancelled before it starts, and the balancer moves it very incrementally. So if you start seeing a problem, you can just turn off the balancer while you investigate. You might also crank down how big a bite the balancer will take in one shot. ceph config set mgr target_max_misplaced_ratio .01 > On Jul 1, 2026, at 9:03 AM, Eugen Block via ceph-users <ceph-users(a)ceph.io> wrote: > > Hi, > > I would try to avoid adding a host with only few OSDs if other hosts are equipped differently. Although I haven't checked in a while I don't expect the behavior to have changed in recent versions. > > So here's my theory: If you add a new host with only one or two OSDs, Ceph can assign many more PGs than average to the first up OSD in order to comply with failure domain (probably host). Same goes for the last OSD during shut down. We had a related case four years ago when we tried to rebuild OSD nodes in a customer cluster. Since the customer cluster was still on default values for mon_max_pg_per_osd and osd_max_pg_per_osd_hard_ratio, the (too many) assigned PGs led to inactive PGs: > >> maybe_wait_for_max_pg withhold creation of pg 75.56s16: 750 >= 750 > > When more OSDs were created on that host (ceph-volume does that sequentially), the issue resolved eventually, except for some inactive PGs, failing the MGR resolved those as well. Since you have around 360 PGs per OSD in average, I assume you increased mon_max_pg_per_osd (default 250), maybe also osd_max_pg_per_osd_hard_ratio (default 3), you most likely dodged the "inactive PG" bullet. > > So my recommendation would be to rather add the hosts with all OSDs at the same time but with crush weight 0. That way you have time to inspect the outcome (for example with dedicated DB/WAL devices you can check if they were created according to the specs). Then reweight the OSDs to the correct value, some users do that gradually to prevent an overload. > > Note the recent discussion about osd heartbeats when adding multiple hosts at once: > > https://lists.ceph.io/hyperkitty/list/ceph-users@ceph.io/thread/RHVPS247M4E… > > Regards, > Eugen > > Zitat von Robert Lukan via ceph-users <ceph-users(a)ceph.io>: > >> Hi everyone, >> >> We are currently in the middle of migrating our infrastructure to a >> Proxmox/Ceph stack and ran into a concerning edge case while expanding the >> cluster. I am hoping to get some advice on the safest way to handle this >> without risking a nearfull OSD. >> >> *The Topology & Situation:* >> >> *Existing:* 5 hosts (proxmox-01 to proxmox-05), each with 8x 7TB SSDs. >> >> *Expansion:* Added a new host (proxmox-08) with 2x 7TB SSDs (osd.40 and >> osd.41). >> >> *Cluster Average:* ~360 PGs per OSD, ~60% utilization. >> >> *Ceph Version:* Squid 19.2.3 >> >> The last time we were expanding the cluster, we had issues when expanding >> it with many OSDs at the same time(it was a memory problem on a host), so >> we decided to be more careful and add 2 disks at the time. >> >> During the backfill phase, we noticed osd.40 catching significantly more >> PGs than osd.41. We paused the migration by setting the nobackfill flag to >> prevent a potential nearfull situation. >> >> *The Current State (ceph osd df):* >> >> osd.40: 423 PGs, 72.56% used, >> >> osd.41: 307 PGs, 51.87% used, >> >> We had 218 PGs sitting in active+remapped+backfill_wait. At that stage we >> have paused the backfill. >> >> If we were to unset nobackfill, the incoming data for those 218 PGs would >> risk pushing osd.40 past the 85% nearfull threshold. However, our >> balancer refused to generate any optimization plans. It reports: >> "optimize_result": >> "Unable to find further optimization... or distribution is already perfect" >> >> We "understand" why this is happening: the balancer is evaluating only when >> backfilling is done. However, it is completely ignoring the transient acting >> state, which was heavily overloading osd.40 >> >> *Our Temporary Workaround:* To prevent the potential issue, we have >> temporarily set the reweight of osd.40 to 0 (effectively draining it out) >> so we can safely lift the nobackfill flag and let the cluster settle >> without hitting capacity limits. >> >> *My Questions for the Community:* >> >> What is the standard best practice for handling this "small bucket" >> transient imbalance when adding a small number of OSDs to a new host? Or is >> this just a bad idea in general ? >> >> Is there a way to force the built-in upmap balancer to respect the >> transient/acting capacity of an OSD so it doesn't allow a drive to go >> towards 85% during a migration? I understand we were not there, but being >> 12 % away was "close" enough. >> >> One of the ideas was to reweight the offending OSD, to remove a few PGs, so >> it would not be so close to nearfull situation. But this approach is >> tedious and requires "baby-sitting". >> >> I guess this might be a good candidate for upmap remap script, but we were >> not "brave" enough to run in it a production environment the first time. >> >> Thanks, >> >> Robert >> _______________________________________________ >> ceph-users mailing list -- ceph-users(a)ceph.io >> To unsubscribe send an email to ceph-users-leave(a)ceph.io > > > _______________________________________________ > ceph-users mailing list -- ceph-users(a)ceph.io > To unsubscribe send an email to ceph-users-leave(a)ceph.io

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