Massive mon slow-ops when restarting mon daemons
Hey there! I’m currently in the process of upgrading the production cluster from v18.2.8 -> v19.2.6 via „ceph orch upgrade“. I tested this upgrade in our staging environment and everything went great. On our production environment I encounter some worrisome issues with the mon daemons. The cluster itself: 5x MON Daemons 5x MGR Daemons 1500x OSD - 2 larger Pools with each 16k in PG. … so a somewhat larger cluster. The orchestrator started re-deploying the MGR, which went fine. During the MON redeployment, the cluster went into warning with messages like „34846 slow ops. mon.mon1 has slow ops“. The counter climbed rapidly. Only way to stop this was to restart the MON in question. Sometimes I had to restart the MON multiple times. Afterwards the cluster is healthy again….until I restart any MON. The symptoms return until restarting fixes it again. I tried to dump the mon_ops_in_flight, but the command just hangs (probably because of the large error count). Filtering the journal for the issues: ``` journalctl -g "oldest is" --since "3 hours ago" -u ceph-d8a6f365-99de-42f2-b32b-c9ea11df945c@mon.partnach <mailto:ceph-d8a6f365-99de-42f2-b32b-c9ea11df945c@mon.partnach> Sep 14 09:45:05 partnach conmon[1735]: 2026-09-14T07:45:05.331+0000 7fe90bfaf640 -1 mon.partnach@0(leader) e78 get_health_metrics reporting 18286 slow ops, oldest is log(1000 entries from seq 2 at 2026-08-26T04:51:47.819315+0000) Sep 14 09:45:10 partnach ceph-mon[1742]: mon.partnach@0(leader) e78 get_health_metrics reporting 18505 slow ops, oldest is log(1000 entries from seq 4003 at 2026-09-11T12:25:52.136679+0000) Sep 14 09:45:10 partnach conmon[1735]: 2026-09-14T07:45:10.827+0000 7fe90bfaf640 -1 mon.partnach@0(leader) e78 get_health_metrics reporting 18505 slow ops, oldest is log(1000 entries from seq 4003 at 2026-09-11T12:25:52.136679+0000) Sep 14 09:45:15 partnach ceph-mon[1742]: mon.partnach@0(leader) e78 get_health_metrics reporting 18671 slow ops, oldest is log(1000 entries from seq 2002 at 2026-09-07T16:47:58.529125+0000) Sep 14 09:45:15 partnach conmon[1735]: 2026-09-14T07:45:15.924+0000 7fe90bfaf640 -1 mon.partnach@0(leader) e78 get_health_metrics reporting 18671 slow ops, oldest is log(1000 entries from seq 2002 at 2026-09-07T16:47:58.529125+0000) Sep 14 09:45:21 partnach ceph-mon[1742]: mon.partnach@0(leader) e78 get_health_metrics reporting 18814 slow ops, oldest is log(1000 entries from seq 2002 at 2026-09-10T20:12:26.565558+0000) Sep 14 09:45:21 partnach conmon[1735]: 2026-09-14T07:45:21.224+0000 7fe90bfaf640 -1 mon.partnach@0(leader) e78 get_health_metrics reporting 18814 slow ops, oldest is log(1000 entries from seq 2002 at 2026-09-10T20:12:26.565558+0000) Sep 14 09:45:26 partnach ceph-mon[1742]: mon.partnach@0(leader) e78 get_health_metrics reporting 19042 slow ops, oldest is log(1000 entries from seq 1002 at 2026-09-10T14:13:26.625340+0000) Sep 14 09:45:26 partnach conmon[1735]: 2026-09-14T07:45:26.700+0000 7fe90bfaf640 -1 mon.partnach@0(leader) e78 get_health_metrics reporting 19042 slow ops, oldest is log(1000 entries from seq 1002 at 2026-09-10T14:13:26.625340+0000) Sep 14 09:45:32 partnach ceph-mon[1742]: mon.partnach@0(leader) e78 get_health_metrics reporting 19280 slow ops, oldest is log(1000 entries from seq 2002 at 2026-09-13T08:23:50.558481+0000) Sep 14 09:45:32 partnach conmon[1735]: 2026-09-14T07:45:32.432+0000 7fe90bfaf640 -1 mon.partnach@0(leader) e78 get_health_metrics reporting 19280 slow ops, oldest is log(1000 entries from seq 2002 at 2026-09-13T08:23:50.558481+0000) Sep 14 09:45:37 partnach ceph-mon[1742]: mon.partnach@0(leader) e78 get_health_metrics reporting 19433 slow ops, oldest is log(1000 entries from seq 1002 at 2026-09-11T20:28:14.104877+0000) Sep 14 09:45:37 partnach conmon[1735]: 2026-09-14T07:45:37.568+0000 7fe90bfaf640 -1 mon.partnach@0(leader) e78 get_health_metrics reporting 19433 slow ops, oldest is log(1000 entries from seq 1002 at 2026-09-11T20:28:14.104877+0000) Sep 14 09:45:43 partnach ceph-mon[1742]: mon.partnach@0(leader) e78 get_health_metrics reporting 19632 slow ops, oldest is log(1000 entries from seq 2 at 2026-09-10T08:47:13.259138+0000) Sep 14 09:45:43 partnach conmon[1735]: 2026-09-14T07:45:43.292+0000 7fe90bfaf640 -1 mon.partnach@0(leader) e78 get_health_metrics reporting 19632 slow ops, oldest is log(1000 entries from seq 2 at 2026-09-10T08:47:13.259138+0000) ``` I’m not quite sure what the lock is here. The mon tries to store some old cluster log entries from various dates? Checked the underlying network fabric, CPU load, clock skew, compacted the rocksdb manually on each mon ect. All is fine. I also set "ceph config set global mon_cluster_log_level info“ **before** the 10th of September. Luckily the upgrade has finished with the MON daemons and is now re-deploying all OSDs. Does anyone know whats going on? Some kind of old hanging Log-Entries? Best Regards, Alex Walender --------------------------- M.Sc Alex Walender Institut für Bio- und Geowissenschaften IBG 5 - Computergestützte Metagenomik / de.NBI Cloud Site Bielefeld Büro : Universität Bielefeld (UHG), N7-101 Tel. : +49-521-106-2907 Forschungszentrum Jülich GmbH 52425 Jülich Sitz der Gesellschaft: Jülich Eingetragen im Handelsregister des Amtsgerichts Düren Nr. HR B 3498 Vorsitzender des Aufsichtsrats: MinDir Stefan Müller Geschäftsführung: Prof. Dr. Astrid Lambrecht (Vorsitzende), Dr. Stephanie Bauer (stellv. Vorsitzende), Prof. Dr. Ir. Pieter Jansens
On 14/09/2026 10:53, Alex Walender wrote:
Hey there!
I’m currently in the process of upgrading the production cluster from v18.2.8 -> v19.2.6 via „ceph orch upgrade“. I tested this upgrade in our staging environment and everything went great. On our production environment I encounter some worrisome issues with the mon daemons.
The cluster itself: 5x MON Daemons 5x MGR Daemons 1500x OSD - 2 larger Pools with each 16k in PG. … so a somewhat larger cluster.
The orchestrator started re-deploying the MGR, which went fine. During the MON redeployment, the cluster went into warning with messages like „34846 slow ops. mon.mon1 has slow ops“. The counter climbed rapidly. Only way to stop this was to restart the MON in question. Sometimes I had to restart the MON multiple times. Afterwards the cluster is healthy again….until I restart any MON. The symptoms return until restarting fixes it again.
I tried to dump the mon_ops_in_flight, but the command just hangs (probably because of the large error count).
Hello, We have a somewhat similar issue on a, busy, CephFS cluster with 1500 OSDs (5 MON+MGR, 7 MDS -- 5 of which are also MON+MGR, 52 OSD nodes, largest pool with 8K PGs). This is an upgrade from 17.2.8 to 19.2.6. We did a staggered upgrade to be able to upgrade the 7 MDS during our next scheduled downtime (with "mgr/orchestrator/fail_fs"), since we have 6 active MDS. The MGR, MON & "crash" upgrades went smoothly, but there were issues during the OSD upgrades (after 24+ hours, about 60% of the OSD updated), and the MONs started to stall: 2266 slow ops, oldest one blocked for 153 sec, mon.$MON0 has slow ops and sometime the MONs did not answer at all: 2026-09-16T12:17:26.485+0000 7f7972084640 -1 monclient: get_monmap_and_config failed to get config Pausing the upgrade seemed to worsen the MONs issues ("159104 slow ops, oldest one blocked for 951 sec, mon.$MON0 has slow ops"), so we resumed it to its completion (41 hours for MGR+MON+crash+1500 OSDs). Sometimes the MON issue goes away on its own, or we have to fail/restart MON(s) to get back to a "normal" situation. This continues even now, after all OSDs have been upgraded & only the MDS (+one RGW) remain in the older version until our scheduled downtime: "overall": { "ceph version 17.2.8 (f817ceb7f187defb1d021d6328fa833eb8e943b3) quincy (stable)": 8, "ceph version 19.2.6 (f9fd95b4335bad6a26d7a74468f55d269e8dbef4) squid (stable)": 1540 } The frequency of the issue is every ~3 hours for this cluster. We see thousands of: "Sep 17 10:25:15 $MON1 ceph-mon[2618906]: ReplicaActive::clear_remote_reservation(): not reserved!" in the MON logs. We had no issue upgrading two smaller clusters (non-staggered upgrades), one with 150 OSDs and another with 800 OSDs (both clusters were already running Squid). Loïc. PS: We find that there are multiple issues with the upgrade process, like: - OSDs in an alternate CRUSH tree were forcibly moved to the "default" branch after their upgrade (on nodes with OSDs in 2 independent CRUSH trees: "default" and "fast" -- no issue on nodes with all OSDs in an alternate CRUSH tree) - the update documentation is lacking regarding the update of the credentials created by "cephadm" itself (bootstrap, admin, deployed services, ...) and, were it not for Eugen B., we probably wouldn't have found "mon_auth_emergency_allowed_ciphers" - progress messages (displayed by "ceph -W cephadm") have a problem with instance counters (all instances of whatever is being updated are displayed as the first instance, there "1/59"), which is a confusing: 2026-09-15T09:11:18.662822+0000 mgr.$MGR1.osnxsd [INF] Upgrade: Updating crash.$NODE7 (1/59) [...] 2026-09-15T09:11:41.166019+0000 mgr.$MGR1.osnxsd [INF] Upgrade: Updating crash.$NODE8 (1/59) (in "src/pybind/mgr/cephadm/upgrade.py", "_upgrade_daemons()": "num" is set to "1" but never incremented in the loop) -- | Loic Tortay <tortay@cc.in2p3.fr> - IN2P3 Computing Centre |
I don't have anything to contribute to resolve this, I just wanted to report that I've been observing mon slow ops every now and then as well (way earlier than Squid). IIRC, those were also during Ceph upgrades, but they never were reproducible so I've never got to investigate them properly. I haven't seen that number range yet (5 or 6 digits) but what usually helped was to restart the affected mon, sometimes multiple restarts were required as you already stated as well. I have several suscpicions but without any evidence, so it's just speculation.
- OSDs in an alternate CRUSH tree were forcibly moved to the "default" branch after their upgrade (on nodes with OSDs in 2 independent CRUSH trees: "default" and "fast" -- no issue on nodes with all OSDs in an alternate CRUSH tree)
This is worrying, I haven't read anything like this yet on this list. Could it help to set osd_crush_update_on_start to false? I'd like to test this but I'm not sure when I'll have the time for it.
the update documentation is lacking regarding the update of the credentials created by "cephadm" itself (bootstrap, admin, deployed services, ...) and, were it not for Eugen B., we probably wouldn't have found "mon_auth_emergency_allowed_ciphers"
Thanks for the credits, but mon_auth_emergency_allowed_ciphers is documented. ;-) https://docs.ceph.com/en/latest/rados/configuration/auth-config-ref/index.ht...
progress messages (displayed by "ceph -W cephadm") have a problem with instance counters (all instances of whatever is being updated are displayed as the first instance, there "1/59"), which is a confusing: 2026-09-15T09:11:18.662822+0000 mgr.$MGR1.osnxsd [INF] Upgrade: Updating crash.$NODE7 (1/59)
I haven't watched it yet with ceph -W cephadm, but this might explain why one of our customers was constantly failing mgr in their staging environment because they didn't see progress in 'ceph orch ps' output. This potentially lead to an incomplete upgrade (AUTH_INSECURE_SERVICE_TICKETS didn't clear, looking at the other thread it might have been enough to simply set 'ceph mon set auth_service_cipher aes256k'). Zitat von Loïc Tortay <ceph-users@ceph.io>:
On 14/09/2026 10:53, Alex Walender wrote:
Hey there!
I’m currently in the process of upgrading the production cluster from v18.2.8 -> v19.2.6 via „ceph orch upgrade“. I tested this upgrade in our staging environment and everything went great. On our production environment I encounter some worrisome issues with the mon daemons.
The cluster itself: 5x MON Daemons 5x MGR Daemons 1500x OSD - 2 larger Pools with each 16k in PG. … so a somewhat larger cluster.
The orchestrator started re-deploying the MGR, which went fine. During the MON redeployment, the cluster went into warning with messages like „34846 slow ops. mon.mon1 has slow ops“. The counter climbed rapidly. Only way to stop this was to restart the MON in question. Sometimes I had to restart the MON multiple times. Afterwards the cluster is healthy again….until I restart any MON. The symptoms return until restarting fixes it again.
I tried to dump the mon_ops_in_flight, but the command just hangs (probably because of the large error count).
Hello, We have a somewhat similar issue on a, busy, CephFS cluster with 1500 OSDs (5 MON+MGR, 7 MDS -- 5 of which are also MON+MGR, 52 OSD nodes, largest pool with 8K PGs).
This is an upgrade from 17.2.8 to 19.2.6. We did a staggered upgrade to be able to upgrade the 7 MDS during our next scheduled downtime (with "mgr/orchestrator/fail_fs"), since we have 6 active MDS.
The MGR, MON & "crash" upgrades went smoothly, but there were issues during the OSD upgrades (after 24+ hours, about 60% of the OSD updated), and the MONs started to stall: 2266 slow ops, oldest one blocked for 153 sec, mon.$MON0 has slow ops and sometime the MONs did not answer at all: 2026-09-16T12:17:26.485+0000 7f7972084640 -1 monclient: get_monmap_and_config failed to get config
Pausing the upgrade seemed to worsen the MONs issues ("159104 slow ops, oldest one blocked for 951 sec, mon.$MON0 has slow ops"), so we resumed it to its completion (41 hours for MGR+MON+crash+1500 OSDs).
Sometimes the MON issue goes away on its own, or we have to fail/restart MON(s) to get back to a "normal" situation.
This continues even now, after all OSDs have been upgraded & only the MDS (+one RGW) remain in the older version until our scheduled downtime: "overall": { "ceph version 17.2.8 (f817ceb7f187defb1d021d6328fa833eb8e943b3) quincy (stable)": 8, "ceph version 19.2.6 (f9fd95b4335bad6a26d7a74468f55d269e8dbef4) squid (stable)": 1540 } The frequency of the issue is every ~3 hours for this cluster.
We see thousands of: "Sep 17 10:25:15 $MON1 ceph-mon[2618906]: ReplicaActive::clear_remote_reservation(): not reserved!" in the MON logs.
We had no issue upgrading two smaller clusters (non-staggered upgrades), one with 150 OSDs and another with 800 OSDs (both clusters were already running Squid).
Loïc.
PS: We find that there are multiple issues with the upgrade process, like: - OSDs in an alternate CRUSH tree were forcibly moved to the "default" branch after their upgrade (on nodes with OSDs in 2 independent CRUSH trees: "default" and "fast" -- no issue on nodes with all OSDs in an alternate CRUSH tree) - the update documentation is lacking regarding the update of the credentials created by "cephadm" itself (bootstrap, admin, deployed services, ...) and, were it not for Eugen B., we probably wouldn't have found "mon_auth_emergency_allowed_ciphers" - progress messages (displayed by "ceph -W cephadm") have a problem with instance counters (all instances of whatever is being updated are displayed as the first instance, there "1/59"), which is a confusing: 2026-09-15T09:11:18.662822+0000 mgr.$MGR1.osnxsd [INF] Upgrade: Updating crash.$NODE7 (1/59) [...] 2026-09-15T09:11:41.166019+0000 mgr.$MGR1.osnxsd [INF] Upgrade: Updating crash.$NODE8 (1/59) (in "src/pybind/mgr/cephadm/upgrade.py", "_upgrade_daemons()": "num" is set to "1" but never incremented in the loop) -- | Loic Tortay <tortay@cc.in2p3.fr> - IN2P3 Computing Centre | _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io
Hi I currently experience the same as described in the subject: “Massive mon slow-ops when restarting mon daemons” - This is not as a part of Ceph upgrade, just plain reboots. The cluster runs 5 MONs with ~1K OSDs at 18.2.8 - And it’s always the same MON host that has rapid increasing number of SLOW OPS. Logging shows the same kinda messages as reported by Alex Walander “… get_health_metrics reporting 18814 slow ops, oldest is log(1000 entries from seq 2002 at 2026-09-10T20:12:26.565558+0000)” I did not see this issue when running 18.2.7, but it was seen from the first reboot after upgrading to 18.2.8 (and ever since) - I suspect the root cause might have been introduced in that release. BR. Kasper On 6 Oct 2026, at 08.34, Eugen Block <ceph-users@ceph.io> wrote: I don't have anything to contribute to resolve this, I just wanted to report that I've been observing mon slow ops every now and then as well (way earlier than Squid). IIRC, those were also during Ceph upgrades, but they never were reproducible so I've never got to investigate them properly. I haven't seen that number range yet (5 or 6 digits) but what usually helped was to restart the affected mon, sometimes multiple restarts were required as you already stated as well. I have several suscpicions but without any evidence, so it's just speculation. - OSDs in an alternate CRUSH tree were forcibly moved to the "default" branch after their upgrade (on nodes with OSDs in 2 independent CRUSH trees: "default" and "fast" -- no issue on nodes with all OSDs in an alternate CRUSH tree) This is worrying, I haven't read anything like this yet on this list. Could it help to set osd_crush_update_on_start to false? I'd like to test this but I'm not sure when I'll have the time for it. the update documentation is lacking regarding the update of the credentials created by "cephadm" itself (bootstrap, admin, deployed services, ...) and, were it not for Eugen B., we probably wouldn't have found "mon_auth_emergency_allowed_ciphers" Thanks for the credits, but mon_auth_emergency_allowed_ciphers is documented. ;-) https://docs.ceph.com/en/latest/rados/configuration/auth-config-ref/index.ht... progress messages (displayed by "ceph -W cephadm") have a problem with instance counters (all instances of whatever is being updated are displayed as the first instance, there "1/59"), which is a confusing: 2026-09-15T09:11:18.662822+0000 mgr.$MGR1.osnxsd [INF] Upgrade: Updating crash.$NODE7 (1/59) I haven't watched it yet with ceph -W cephadm, but this might explain why one of our customers was constantly failing mgr in their staging environment because they didn't see progress in 'ceph orch ps' output. This potentially lead to an incomplete upgrade (AUTH_INSECURE_SERVICE_TICKETS didn't clear, looking at the other thread it might have been enough to simply set 'ceph mon set auth_service_cipher aes256k'). Zitat von Loïc Tortay <ceph-users@ceph.io>: On 14/09/2026 10:53, Alex Walender wrote: Hey there! I’m currently in the process of upgrading the production cluster from v18.2.8 -> v19.2.6 via „ceph orch upgrade“. I tested this upgrade in our staging environment and everything went great. On our production environment I encounter some worrisome issues with the mon daemons. The cluster itself: 5x MON Daemons 5x MGR Daemons 1500x OSD - 2 larger Pools with each 16k in PG. … so a somewhat larger cluster. The orchestrator started re-deploying the MGR, which went fine. During the MON redeployment, the cluster went into warning with messages like „34846 slow ops. mon.mon1 has slow ops“. The counter climbed rapidly. Only way to stop this was to restart the MON in question. Sometimes I had to restart the MON multiple times. Afterwards the cluster is healthy again….until I restart any MON. The symptoms return until restarting fixes it again. I tried to dump the mon_ops_in_flight, but the command just hangs (probably because of the large error count). Hello, We have a somewhat similar issue on a, busy, CephFS cluster with 1500 OSDs (5 MON+MGR, 7 MDS -- 5 of which are also MON+MGR, 52 OSD nodes, largest pool with 8K PGs). This is an upgrade from 17.2.8 to 19.2.6. We did a staggered upgrade to be able to upgrade the 7 MDS during our next scheduled downtime (with "mgr/orchestrator/fail_fs"), since we have 6 active MDS. The MGR, MON & "crash" upgrades went smoothly, but there were issues during the OSD upgrades (after 24+ hours, about 60% of the OSD updated), and the MONs started to stall: 2266 slow ops, oldest one blocked for 153 sec, mon.$MON0 has slow ops and sometime the MONs did not answer at all: 2026-09-16T12:17:26.485+0000 7f7972084640 -1 monclient: get_monmap_and_config failed to get config Pausing the upgrade seemed to worsen the MONs issues ("159104 slow ops, oldest one blocked for 951 sec, mon.$MON0 has slow ops"), so we resumed it to its completion (41 hours for MGR+MON+crash+1500 OSDs). Sometimes the MON issue goes away on its own, or we have to fail/restart MON(s) to get back to a "normal" situation. This continues even now, after all OSDs have been upgraded & only the MDS (+one RGW) remain in the older version until our scheduled downtime: "overall": { "ceph version 17.2.8 (f817ceb7f187defb1d021d6328fa833eb8e943b3) quincy (stable)": 8, "ceph version 19.2.6 (f9fd95b4335bad6a26d7a74468f55d269e8dbef4) squid (stable)": 1540 } The frequency of the issue is every ~3 hours for this cluster. We see thousands of: "Sep 17 10:25:15 $MON1 ceph-mon[2618906]: ReplicaActive::clear_remote_reservation(): not reserved!" in the MON logs. We had no issue upgrading two smaller clusters (non-staggered upgrades), one with 150 OSDs and another with 800 OSDs (both clusters were already running Squid). Loïc. PS: We find that there are multiple issues with the upgrade process, like: - OSDs in an alternate CRUSH tree were forcibly moved to the "default" branch after their upgrade (on nodes with OSDs in 2 independent CRUSH trees: "default" and "fast" -- no issue on nodes with all OSDs in an alternate CRUSH tree) - the update documentation is lacking regarding the update of the credentials created by "cephadm" itself (bootstrap, admin, deployed services, ...) and, were it not for Eugen B., we probably wouldn't have found "mon_auth_emergency_allowed_ciphers" - progress messages (displayed by "ceph -W cephadm") have a problem with instance counters (all instances of whatever is being updated are displayed as the first instance, there "1/59"), which is a confusing: 2026-09-15T09:11:18.662822+0000 mgr.$MGR1.osnxsd [INF] Upgrade: Updating crash.$NODE7 (1/59) [...] 2026-09-15T09:11:41.166019+0000 mgr.$MGR1.osnxsd [INF] Upgrade: Updating crash.$NODE8 (1/59) (in "src/pybind/mgr/cephadm/upgrade.py", "_upgrade_daemons()": "num" is set to "1" but never incremented in the loop) -- | Loic Tortay <tortay@cc.in2p3.fr> - IN2P3 Computing Centre | _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io
Hey, it probably has to do something with the size of a cluster. I also run a staging cluster with only 3 nodes with the same deployment and config. I never saw the issue there. Your cluster also seems quite big. The thing that „bloats“ the health messages during the upgrade are definitely the warnings about the weak key ciphers. Maybe the MONs are stumbling about the size of that. --------------------------- M.Sc Alex Walender Institut für Bio- und Geowissenschaften IBG 5 - Computergestützte Metagenomik / de.NBI Cloud Site Bielefeld Büro : Universität Bielefeld (UHG), N7-101 Tel. : +49-521-106-2907 Forschungszentrum Jülich GmbH 52425 Jülich Sitz der Gesellschaft: Jülich Eingetragen im Handelsregister des Amtsgerichts Düren Nr. HR B 3498 Vorsitzender des Aufsichtsrats: MinDir Stefan Müller Geschäftsführung: Prof. Dr. Astrid Lambrecht (Vorsitzende), Dr. Stephanie Bauer (stellv. Vorsitzende), Prof. Dr. Ir. Pieter Jansens
Am 26.10.2026 um 22:06 schrieb Kasper Rasmussen <ceph-users@ceph.io>:
Hi
I currently experience the same as described in the subject: “Massive mon slow-ops when restarting mon daemons” - This is not as a part of Ceph upgrade, just plain reboots.
The cluster runs 5 MONs with ~1K OSDs at 18.2.8 - And it’s always the same MON host that has rapid increasing number of SLOW OPS. Logging shows the same kinda messages as reported by Alex Walander
“… get_health_metrics reporting 18814 slow ops, oldest is log(1000 entries from seq 2002 at 2026-09-10T20:12:26.565558+0000)”
I did not see this issue when running 18.2.7, but it was seen from the first reboot after upgrading to 18.2.8 (and ever since) - I suspect the root cause might have been introduced in that release.
BR. Kasper
On 6 Oct 2026, at 08.34, Eugen Block <ceph-users@ceph.io> wrote:
I don't have anything to contribute to resolve this, I just wanted to report that I've been observing mon slow ops every now and then as well (way earlier than Squid). IIRC, those were also during Ceph upgrades, but they never were reproducible so I've never got to investigate them properly. I haven't seen that number range yet (5 or 6 digits) but what usually helped was to restart the affected mon, sometimes multiple restarts were required as you already stated as well. I have several suscpicions but without any evidence, so it's just speculation.
- OSDs in an alternate CRUSH tree were forcibly moved to the "default" branch after their upgrade (on nodes with OSDs in 2 independent CRUSH trees: "default" and "fast" -- no issue on nodes with all OSDs in an alternate CRUSH tree)
This is worrying, I haven't read anything like this yet on this list. Could it help to set osd_crush_update_on_start to false? I'd like to test this but I'm not sure when I'll have the time for it.
the update documentation is lacking regarding the update of the credentials created by "cephadm" itself (bootstrap, admin, deployed services, ...) and, were it not for Eugen B., we probably wouldn't have found "mon_auth_emergency_allowed_ciphers"
Thanks for the credits, but mon_auth_emergency_allowed_ciphers is documented. ;-) https://docs.ceph.com/en/latest/rados/configuration/auth-config-ref/index.ht...
progress messages (displayed by "ceph -W cephadm") have a problem with instance counters (all instances of whatever is being updated are displayed as the first instance, there "1/59"), which is a confusing: 2026-09-15T09:11:18.662822+0000 mgr.$MGR1.osnxsd [INF] Upgrade: Updating crash.$NODE7 (1/59)
I haven't watched it yet with ceph -W cephadm, but this might explain why one of our customers was constantly failing mgr in their staging environment because they didn't see progress in 'ceph orch ps' output. This potentially lead to an incomplete upgrade (AUTH_INSECURE_SERVICE_TICKETS didn't clear, looking at the other thread it might have been enough to simply set 'ceph mon set auth_service_cipher aes256k').
Zitat von Loïc Tortay <ceph-users@ceph.io>:
On 14/09/2026 10:53, Alex Walender wrote: Hey there!
I’m currently in the process of upgrading the production cluster from v18.2.8 -> v19.2.6 via „ceph orch upgrade“. I tested this upgrade in our staging environment and everything went great. On our production environment I encounter some worrisome issues with the mon daemons.
The cluster itself: 5x MON Daemons 5x MGR Daemons 1500x OSD - 2 larger Pools with each 16k in PG. … so a somewhat larger cluster.
The orchestrator started re-deploying the MGR, which went fine. During the MON redeployment, the cluster went into warning with messages like „34846 slow ops. mon.mon1 has slow ops“. The counter climbed rapidly. Only way to stop this was to restart the MON in question. Sometimes I had to restart the MON multiple times. Afterwards the cluster is healthy again….until I restart any MON. The symptoms return until restarting fixes it again.
I tried to dump the mon_ops_in_flight, but the command just hangs (probably because of the large error count).
Hello, We have a somewhat similar issue on a, busy, CephFS cluster with 1500 OSDs (5 MON+MGR, 7 MDS -- 5 of which are also MON+MGR, 52 OSD nodes, largest pool with 8K PGs).
This is an upgrade from 17.2.8 to 19.2.6. We did a staggered upgrade to be able to upgrade the 7 MDS during our next scheduled downtime (with "mgr/orchestrator/fail_fs"), since we have 6 active MDS.
The MGR, MON & "crash" upgrades went smoothly, but there were issues during the OSD upgrades (after 24+ hours, about 60% of the OSD updated), and the MONs started to stall: 2266 slow ops, oldest one blocked for 153 sec, mon.$MON0 has slow ops and sometime the MONs did not answer at all: 2026-09-16T12:17:26.485+0000 7f7972084640 -1 monclient: get_monmap_and_config failed to get config
Pausing the upgrade seemed to worsen the MONs issues ("159104 slow ops, oldest one blocked for 951 sec, mon.$MON0 has slow ops"), so we resumed it to its completion (41 hours for MGR+MON+crash+1500 OSDs).
Sometimes the MON issue goes away on its own, or we have to fail/restart MON(s) to get back to a "normal" situation.
This continues even now, after all OSDs have been upgraded & only the MDS (+one RGW) remain in the older version until our scheduled downtime: "overall": { "ceph version 17.2.8 (f817ceb7f187defb1d021d6328fa833eb8e943b3) quincy (stable)": 8, "ceph version 19.2.6 (f9fd95b4335bad6a26d7a74468f55d269e8dbef4) squid (stable)": 1540 } The frequency of the issue is every ~3 hours for this cluster.
We see thousands of: "Sep 17 10:25:15 $MON1 ceph-mon[2618906]: ReplicaActive::clear_remote_reservation(): not reserved!" in the MON logs.
We had no issue upgrading two smaller clusters (non-staggered upgrades), one with 150 OSDs and another with 800 OSDs (both clusters were already running Squid).
Loïc.
PS: We find that there are multiple issues with the upgrade process, like: - OSDs in an alternate CRUSH tree were forcibly moved to the "default" branch after their upgrade (on nodes with OSDs in 2 independent CRUSH trees: "default" and "fast" -- no issue on nodes with all OSDs in an alternate CRUSH tree) - the update documentation is lacking regarding the update of the credentials created by "cephadm" itself (bootstrap, admin, deployed services, ...) and, were it not for Eugen B., we probably wouldn't have found "mon_auth_emergency_allowed_ciphers" - progress messages (displayed by "ceph -W cephadm") have a problem with instance counters (all instances of whatever is being updated are displayed as the first instance, there "1/59"), which is a confusing: 2026-09-15T09:11:18.662822+0000 mgr.$MGR1.osnxsd [INF] Upgrade: Updating crash.$NODE7 (1/59) [...] 2026-09-15T09:11:41.166019+0000 mgr.$MGR1.osnxsd [INF] Upgrade: Updating crash.$NODE8 (1/59) (in "src/pybind/mgr/cephadm/upgrade.py", "_upgrade_daemons()": "num" is set to "1" but never incremented in the loop) -- | Loic Tortay <tortay@cc.in2p3.fr> - IN2P3 Computing Centre | _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io
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participants (4)
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Alex Walender
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Eugen Block
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Kasper Rasmussen
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Loïc Tortay