Hi Istvan,
Only thing what I have in my mind to increase the replica size from 3 to 5 so it could tollerate more osd slowness with size 5 min_size 2.
I wouldn't do that, it will only get worse as every write IO will have to wait for 2 mores OSDs to ACK and the slow ops you've seen refer to write IOs (looping over "waiting for rw locks"). How many NVMe OSDs does this 2048 PGs RGW index pool has? Have you check the num_shards of this bucket that is receiving continuous deletes and uploads 24/7? Regards, Frédéric. ----- Le 14 Nov 24, à 7:16, Istvan Szabo, Agoda <Istvan.Szabo@agoda.com> a écrit :
Hi,
This issue was for us before update also, unluckiuly it's not gone with update 😕 We don't use HDD, only ssd and nvme and the index pool is specifically on nvme. Yes, I tried to set for the value divided by 4, no luck 🙁
Seems like based on metadata okay, however the device class when I've created it I've defined nvme (ceph-volume lvm batch --bluestore --yes --osds-per-device 4 --crush-device-class nvme /dev/sdo) and in the osd tree it is nvme, but I guess it means what it says by default if I don't define anything it would have been ssd. "bluestore_bdev_type": "ssd", "default_device_class": "ssd", "osd_objectstore": "bluestore", "rotational": "0"
Only thing what I have in my mind to increase the replica size from 3 to 5 so it could tollerate more osd slowness with size 5 min_size 2.
Again, thank you again for your ideas.
From: Frédéric Nass <frederic.nass@univ-lorraine.fr> Sent: Wednesday, November 13, 2024 4:32 PM To: Szabo, Istvan (Agoda) <Istvan.Szabo@agoda.com> Cc: Tyler Stachecki <stachecki.tyler@gmail.com>; Ceph Users <ceph-users@ceph.io> Subject: Re: [ceph-users] Re: Slow ops during index pool recovery causes cluster performance drop to 1% Email received from the internet. If in doubt, don't click any link nor open any attachment !
Hi Istvan,
Changing the scheduler to 'wpq' could help you to quickly identify if the issue you're facing is related to 'mclock' or not.
If you stick with mclock, depending on the rotational status of each OSD (ceph osd metadata N | jq -r .rotational), you should set each OSD's spec (osd_mclock_max_capacity_iops_hdd if rotational=1 or osd_mclock_max_capacity_iops_ssd if rotational=0) to the value you calculated, instead of letting the OSD trying to figure out and set a value that may not be accurate, especially with multiple OSDs sharing the same underlying device.
Have you tried setting each OSD's max capacity (ceph config set osd.N osd_mclock_max_capacity_iops_[hdd, ssd])?
Also, make sure the rotational status reported for each OSDs by ceph osd metadata osd.N actually matches the underlying hardware type. This is not always the case depending on how the disks are connected. If it's not, you might have to force it on boot with a udev rule.
Regards, Frédéric.
----- Le 13 Nov 24, à 9:43, Istvan Szabo, Agoda <Istvan.Szabo@agoda.com> a écrit :
Hi Frédéric,
Thank you the ideas.
Cluster is half updated but on the osds which updated are:
"osd_op_queue": "mclock_scheduler", "osd_op_queue_cut_off": "high",
I'd say the value when I do the benchmark how ceph calculates it, it is too high. We have 4 osd on 1 nvme and it sets the value on the last osd from the 4 on nvme which is the highest: 36490.280637
However I changed this value already on some other fully upgraded cluster divided by 4 and didn't help. Buffered io turned on since octopus, didn't change it.
For a quick check that specific osd seems like what you tell:
1 : device size 0x6fc7c00000 : own 0x[40000~4e00000,12f70000~2252d0000,23b060000~21a230000,4583e0000~20f890000,6b1630000~200000000,35a78f0000~478a20000] = 0xccc5b0000 : using 0xa60ed0000(42 GiB) : bluestore has 0x62e79f0000(396 GiB) available wal_total:0, db_total:456087987814, slow_total:0
Istvan
From: Frédéric Nass <frederic.nass@univ-lorraine.fr> Sent: Monday, November 4, 2024 4:14 PM To: Szabo, Istvan (Agoda) <Istvan.Szabo@agoda.com> Cc: Tyler Stachecki <stachecki.tyler@gmail.com>; Ceph Users <ceph-users@ceph.io> Subject: Re: [ceph-users] Re: Slow ops during index pool recovery causes cluster performance drop to 1% Email received from the internet. If in doubt, don't click any link nor open any attachment ! ________________________________
Hi Istvan,
Is you upgraded cluster using wpq or mclock scheduler? (ceph tell osd.X config show | grep osd_op_queue)
Maybe your OSDs set their osd_mclock_max_capacity_iops_* capacity too low on start (ceph config dump | grep osd_mclock_max_capacity_iops) limiting their performance.
You might want to raise these figures if set or go back to wpq to give you enough time to understand how mclock works.
Also, check bluefs_buffered_io as it's default value changed over time. Better run 'true' now (ceph tell osd.X config show | grep bluefs_buffered_io) Also, check for any overspilling as there's been a bug in the past with overspilling not being reported on ceph status (ceph tell osd.X bluefs stats, SLOW line should show 0 Bytes and 0 FILES).
Regards, Frédéric.
----- Le 4 Nov 24, à 5:24, Istvan Szabo, Agoda Istvan.Szabo@agoda.com a écrit :
Hi Tyler,
To be honest we don't have anything set by ourselves regarding compaction and rocksdb: When I check the socket with ceph daemon on nvme and on ssd both have default false on compactL "mon_compact_on_start": "false" "osd_compact_on_start": "false",
Rocksdb also default: bluestore_rocksdb_options": "compression=kNoCompression,max_write_buffer_number=4,min_write_buffer_number_to_merge=1,recycle_log_file_num=4,write_buffer_size=268435456,writable_file_max_buffer_size=0,compaction_readahead_size=2097152,max_background_compactions=2,max_total_wal_size=1073741824"
This is 1 event during the slow ops out of the 20: [ https://gist.githubusercontent.com/Badb0yBadb0y/30de736f5d2bd6ec48aa7acf0a3c... | https://gist.githubusercontent.com/Badb0yBadb0y/30de736f5d2bd6ec48aa7acf0a3c... ]
All belongs to a bucket which doing streaming operation which means continuous delete and upload 24/7.
I can see throttled options but still don't understand why the high latency.
ty
________________________________ From: Tyler Stachecki <stachecki.tyler@gmail.com> Sent: Sunday, November 3, 2024 4:07 PM To: Szabo, Istvan (Agoda) <Istvan.Szabo@agoda.com> Cc: Ceph Users <ceph-users@ceph.io> Subject: Re: [ceph-users] Re: Slow ops during index pool recovery causes cluster performance drop to 1%
Email received from the internet. If in doubt, don't click any link nor open any attachment ! ________________________________
On Sun, Nov 3, 2024 at 1:28 AM Szabo, Istvan (Agoda) <Istvan.Szabo@agoda.com> wrote:
Hi,
I'm updating from octopus to quincy and all in our cluster when index pool recovery kicks off, cluster operation drops to 1%, slow ops comes non-stop. The recovery takes 1-2 hours/nodes.
What I can see the iowait on the nvme drives which belongs to the index pool is pretty high, however the throughput is less than 500MB/s, the iops is less than 5000/sec. ... after update and machine reboot compaction kicks off which generates 30-40 iowait on the node, we prevent with "noup" flag to put these osds into the cluster until compaction finished, however when we have 0 iowait after compaction, I unset noup so recovery can start which causes the above issue. If I wouldn't set noup it would cause even bigger issue.
By any chance, are you specifying a value for bluestore_rocksdb_options in your ceph.conf? The compaction observation at reboot in particular is odd.
Tyler
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