Re: The snaptrim queue of PGs has not decreased for several days.

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ps,

hier the command

[rook@rook-ceph-tools-5459f7cb5b-p55np /]$ ceph pg dump | grep snaptrim | grep -v 'snaptrim_wait' | awk '{print $18}' | sort | uniq
dumped all
0
10
11
2
8
9

Am 20.08.2024 um 10:25 schrieb MARTEL Arnaud:
I had this problem once in the past and found that it was related to a particular osd. To identify it, I ran the command “ceph pg dump | grep snaptrim | grep -v ‘snaptrim_wait’” and found that the osd displayed in the “UP_PRIMARY” column was almost always the same.
So I restarted this osd and that was enough to unblock the snaptrim (the number of snaps in the queue then decreased and, after a few minutes, all snaptrims were completed).

Arnaud

Le 20/08/2024 09:47, « Eugen Block » <eblock@xxxxxx  <mailto:eblock@xxxxxx>> a écrit :


Did you reduce the default values I mentioned? You could also look
into the historic_ops of the primary OSD for one affected PG:


ceph tell osd.<OSD_ID> dump_historic_ops_by_duration


But I'm not sure if that can actually help here. There are plenty of
places to look at, you could turn on debug logs on one primary OSD and
inspect the output.


I just get the feeling that this is one of the corner cases with too
few OSDs, although the cluster load seems to be low.


Zitat von Giovanna Ratini <giovanna.ratini@xxxxxxxxxxxxxxx  <mailto:giovanna.ratini@xxxxxxxxxxxxxxx>>:


Hello Eugen,

yesterday after stop and go of snaptrim the queue decrease a little
and then remain blocked.
They didn't grow and didn't decrease.

Is that good or bad?


Am 19.08.2024 um 15:43 schrieb Eugen Block:
There's a lengthy thread [0] where several approaches are proposed.
The worst is a OSD recreation, but that's the last resort, of course.

What's are the current values for these configs?

ceph config get osd osd_pg_max_concurrent_snap_trims
ceph config get osd osd_max_trimming_pgs

Maybe decrease them to 1 each while the nosnaptrim flag is set,
then unset it. You could also try online (and/or offline osd
compaction) before unsetting the flag. Are the OSD processes
utilizing an entire CPU?

[0]https://www.spinics.net/lists/ceph-users/msg75626.html  <https://www.spinics.net/lists/ceph-users/msg75626.html>

Zitat von Giovanna Ratini <giovanna.ratini@xxxxxxxxxxxxxxx  <mailto:giovanna.ratini@xxxxxxxxxxxxxxx>>:

Hallo Eugen,

yes, the load is for now not too much.

I stop the snap and now this is the output. No changes in the queue.

root@kube-master02:~# k ceph -s
Info: running 'ceph' command with args: [-s]
cluster:
id: 3a35629a-6129-4daf-9db6-36e0eda637c7
health: HEALTH_WARN
nosnaptrim flag(s) set
32 pgs not deep-scrubbed in time
32 pgs not scrubbed in time

services:
mon: 3 daemons, quorum bx,bz,ca (age 30h)
mgr: a(active, since 29h), standbys: b
mds: 1/1 daemons up, 1 hot standby
osd: 6 osds: 6 up (since 21h), 6 in (since 6d)
flags nosnaptrim

data:
volumes: 1/1 healthy
pools: 4 pools, 97 pgs
objects: 4.21M objects, 2.5 TiB
usage: 7.7 TiB used, 76 TiB / 84 TiB avail
pgs: 65 active+clean
32 active+clean+snaptrim_wait

io:
client: 7.4 MiB/s rd, 7.9 MiB/s wr, 11 op/s rd, 35 op/s wr

Am 19.08.2024 um 14:54 schrieb Eugen Block:
What happens when you disable snaptrimming entirely?

ceph osd set nosnaptrim

So the load on your cluster seems low, but are the OSDs heavily
utilized? Have you checked iostat?

Zitat von Giovanna Ratini <giovanna.ratini@xxxxxxxxxxxxxxx  <mailto:giovanna.ratini@xxxxxxxxxxxxxxx>>:

Hello Eugen,

*root@kube-master02:~# k ceph -s*

Info: running 'ceph' command with args: [-s]
cluster:
id: 3a35629a-6129-4daf-9db6-36e0eda637c7
health: HEALTH_WARN
32 pgs not deep-scrubbed in time
32 pgs not scrubbed in time

services:
mon: 3 daemons, quorum bx,bz,ca (age 13h)
mgr: a(active, since 13h), standbys: b
mds: 1/1 daemons up, 1 hot standby
osd: 6 osds: 6 up (since 5h), 6 in (since 5d)

data:
volumes: 1/1 healthy
pools: 4 pools, 97 pgs
objects: 4.20M objects, 2.5 TiB
usage: 7.7 TiB used, 76 TiB / 84 TiB avail
pgs: 65 active+clean
20 active+clean+snaptrim_wait
12 active+clean+snaptrim

io:
client: 3.5 MiB/s rd, 3.6 MiB/s wr, 6 op/s rd, 12 op/s wr

If I understand the documentation correctly, I will never have a
scrub unless the PGs (Placement Groups) are active and clean.

All 32 PGs of the CephFS pool have been in this status for several days:

* 20 active+clean+snaptrim_wait
* 12 active+clean+snaptrim"

Today, I restarted the MON, MGR, and MDS, but no changes in the growing.

Am 18.08.2024 um 18:39 schrieb Eugen Block:
Can you share the current ceph status? Are the OSDs reporting
anything suspicious? How is the disk utilization?

Zitat von Giovanna Ratini <giovanna.ratini@xxxxxxxxxxxxxxx  <mailto:giovanna.ratini@xxxxxxxxxxxxxxx>>:

More information:

The snaptrim take a lot of time but the he objects_trimmed are "0"

"objects_trimmed": 0,
"snaptrim_duration": 500.58076017500002,

It could explain, why the queue are growing up..


Am 17.08.2024 um 14:37 schrieb Giovanna Ratini:
Hello again,

I checked the pgs dump. Snapshot grow up

Query für PG: 3.12
{
"snap_trimq":
"[5b974~3b,5cc3a~1,5cc3c~1,5cc3e~1,5cc40~1,5cd83~1,5cd85~1,5cd87~1,5cd89~1,5cecc~1,5cece~4,5ced3~2,5cf72~1,5cf74~4,5cf79~a2,5d0b8~1,5d0bb~1,5d0bd~a5,5d1f9~2,5d204~a5,5d349~a7,5d48e~3,5d493~a4,5d5d7~a7,5d71e~a3,5d7c2~3,5d860~1,5d865~4,5d86a~a2,5d9aa~1,5d9ac~1,5d9ae~a5,5daf3~a5,5db9a~2,5dc3a~a5,5dce1~1,5dce3~1,5dd81~a7,5dec8~a7,5e00f~a7,5e156~a8,5e29d~1,5e29f~a7,5e3e6~a8,5e52e~a6,5e5d6~2,5e676~a6,5e71e~2,5e7be~a9,5e907~a5,5e9ad~3,5ea50~a7,5eaf9~1,5eafb~1,5eb99~a7,5ec42~2,5ece2~a7,5ed8a~2,5ee2b~a9,5ef74~a7,5f01c~1,5f0bd~a1,5f15f~1,5f161~1,5f163~1,5f167~1,5f206~a1,5f2a8~1,5f2aa~1,5f2ac~1,5f2ae~1,5f34f~a1,5f3f1~1,5f3f3~1,5f3f5~1,5f3f7~1,5f499~a1,5f53b~1,5f53d~1,5f53f~1,5f541~1,5f5e3~a1,5f685~1,5f687~1,5f689~1,5f68d~1,5f72d~a1,5f7cf~1,5f7d1~1,5f7d3~1]",
* "snap_trimq_len": 5421,*
"state": "active+clean+snaptrim",
"epoch": 734130,

Query für PG: 3.12
{
"snap_trimq":
"[5b976~39,5ba53~1,5ba56~a0,5cc3a~1,5cc3c~1,5cc3e~1,5cc40~1,5cd83~1,5cd85~1,5cd87~1,5cd89~1,5cecc~1,5cece~4,5ced3~2,5cf72~1,5cf74~4,5cf79~a2,5d0b8~1,5d0bb~1,5d0bd~a5,5d1f9~2,5d204~a5,5d349~a7,5d48e~3,5d493~a4,5d5d7~a7,5d71e~a3,5d7c2~3,5d860~1,5d865~4,5d86a~a2,5d9aa~1,5d9ac~1,5d9ae~a5,5daf3~a5,5db9a~2,5dc3a~a5,5dce1~1,5dce3~1,5dd81~a7,5dec8~a7,5e00f~a7,5e156~a8,5e29d~1,5e29f~a7,5e3e6~a8,5e52e~a6,5e5d6~2,5e676~a6,5e71e~2,5e7be~a9,5e907~a5,5e9ad~3,5ea50~a7,5eaf9~1,5eafb~1,5eb99~a7,5ec42~2,5ece2~a7,5ed8a~2,5ee2b~a9,5ef74~a7,5f01c~1,5f0bd~a1,5f15f~1,5f161~1,5f163~1,5f167~1,5f206~a1,5f2a8~1,5f2aa~1,5f2ac~1,5f2ae~1,5f34f~a1,5f3f1~1,5f3f3~1,5f3f5~1,5f3f7~1,5f499~a1,5f53b~1,5f53d~1,5f53f~1,5f541~1,5f5e3~a1,5f685~1,5f687~1,5f689~1,5f68d~1,5f72d~a1,5f7cf~1,5f7d1~1,5f7d3~1,5f875~a1]",
* "snap_trimq_len": 5741,*
"state": "active+clean+snaptrim",
"epoch": 734240,
"up": [

Do you know the way to see if the snaptim "process" works?

Best Regard

Gio


Am 17.08.2024 um 12:59 schrieb Giovanna Ratini:
Hello Eugen,

thank you for your answer.

I restarted all the kube-ceph nodes one after the other.
Nothing has changed.

ok, I deactivate the snap ... : ceph fs snap-schedule deactivate /

Is there a way to see how many snapshots will be deleted per hour?

Regards,

Gio





Am 17.08.2024 um 10:12 schrieb Eugen Block:
Hi,

have you tried to fail the mgr? Sometimes the PG stats are
not correct. You could also temporarily disable snapshots
to see if things settle down.

Zitat von Giovanna Ratini <giovanna.ratini@xxxxxxxxxxxxxxx  <mailto:giovanna.ratini@xxxxxxxxxxxxxxx>>:

Hello all,

We use Ceph (v18.2.2) and Rook (1.14.3) as the CSI for a
Kubernetes environment. Last week, we had a problem with
the MDS falling behind on trimming every 4-5 days (GitHub
issue link). We resolved the issue using the steps
outlined in the GitHub issue.

We have 3 hosts (I know, I need to increase this as soon
as possible, and I will!) and 6 OSDs. After running the
commands:

ceph config set mds mds_dir_max_commit_size 80,

ceph fs fail <fs_name>, and

ceph fs set <fs_name> joinable true,

After that, the snaptrim queue for our PGs has stopped
decreasing. All PGs of our CephFS are in either
active+clean+snaptrim_wait or active+clean+snaptrim
states. For example, the PG 3.12 is in the
active+clean+snaptrim state, and its snap_trimq_len was
4077 yesterday but has increased to 4538 today.

I increased the osd_snap_trim_priority to 10 (ceph config
set osd osd_snap_trim_priority 10), but it didn't help.
Only the PGs of our CephFS have this problem.

Do you have any ideas on how we can resolve this issue?

Thanks in advance,
Giovanna
p.s. I'm not a ceph expert :-).
Faulkener asked me for more information, so here it is:
MDS Memory: 11GB
mds_cache_memory_limit: 11,811,160,064 bytes

root@kube-master02:~# ceph fs snap-schedule status /
{
"fs": "rook-cephfs",
"subvol": null,
"path": "/",
"rel_path": "/",
"schedule": "3h",
"retention": {"h": 24, "w": 4},
"start": "2024-05-05T00:00:00",
"created": "2024-05-05T17:28:18",
"first": "2024-05-05T18:00:00",
"last": "2024-08-15T18:00:00",
"last_pruned": "2024-08-15T18:00:00",
"created_count": 817,
"pruned_count": 817,
"active": true
}
I do not understand if the snapshots in the PGs are
correlated with the snapshots on CephFS. Until we
encountered the issue with the "MDS falling behind on
trimming every 4-5 days," we didn't have any problems with
snapshots.

Could someone explain me this or send me to the documentation?
Thank you
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Phone: +49 (0) 7531 88 - 4550

Technical Support
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Giovanna Ratini
Mail:ratini@xxxxxxxxxxxxxxxxxxxxxxxxx  <mailto:ratini@xxxxxxxxxxxxxxxxxxxxxxxxx>
Phone: +49 (0) 7531 88 - 4550

Technical Support
Data Analysis and Visualization Group
Department of Computer and Information Science
University of Konstanz (Box 78)
Universitätsstr. 10
78457 Konstanz, Germany
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Giovanna Ratini
Mail:ratini@xxxxxxxxxxxxxxxxxxxxxxxxx  <mailto:ratini@xxxxxxxxxxxxxxxxxxxxxxxxx>
Phone: +49 (0) 7531 88 - 4550

Technical Support
Data Analysis and Visualization Group
Department of Computer and Information Science
University of Konstanz (Box 78)
Universitätsstr. 10
78457 Konstanz, Germany
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Mail:ratini@xxxxxxxxxxxxxxxxxxxxxxxxx
Phone: +49 (0) 7531 88 - 4550

Technical Support
Data Analysis and Visualization Group
Department of Computer and Information Science
University of Konstanz (Box 78)
Universitätsstr. 10
78457 Konstanz, Germany
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