Re: MDSs report oversized cache during forward scrub

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Hello Frank,

Unfortunately, the ballooning of memory consumed by the MDS is a known issue.

Please add a lot of swap space (as a rough estimate, 2 GB of swap per
1 mln of files stored) to complete the scrub, and ignore the warning.

Yes, there were cases on this list where 2 TB of swap was insufficient.

And yes, the scrub gets automatically canceled if the MDS restarts,
crashes, or kets killed.


On Fri, Jan 10, 2025 at 11:42 PM Frank Schilder <frans@xxxxxx> wrote:
>
> Hi all,
>
> we started a forward scrub on our 5.x PB ceph file system and observe a massive ballooning of MDS caches. Our status is:
>
> # ceph status
>   cluster:
>     id:     xxx
>     health: HEALTH_WARN
>             1 MDSs report oversized cache
>             (muted: MDS_CLIENT_LATE_RELEASE(12d) MDS_CLIENT_RECALL(12d) PG_NOT_DEEP_SCRUBBED(5d) PG_NOT_SCRUBBED(5d) POOL_NEAR_FULL(4w))
>
>   services:
>     mon: 5 daemons, quorum ceph-01,ceph-02,ceph-03,ceph-25,ceph-26 (age 4w)
>     mgr: ceph-03(active, since 3w), standbys: ceph-01, ceph-25, ceph-26, ceph-02
>     mds: 8/8 daemons up, 4 standby
>     osd: 1317 osds: 1316 up (since 5d), 1316 in (since 5w)
>
>   task status:
>     scrub status:
>         mds.ceph-08: active paths [/]
>         mds.ceph-11: active paths [/]
>         mds.ceph-12: active paths [/]
>         mds.ceph-14: active paths [/]
>         mds.ceph-15: active paths [/]
>         mds.ceph-17: active paths [/]
>         mds.ceph-24: active paths [/]
>
>   data:
>     volumes: 1/1 healthy
>     pools:   14 pools, 29161 pgs
>     objects: 4.38G objects, 5.5 PiB
>     usage:   7.2 PiB used, 5.9 PiB / 13 PiB avail
>     pgs:     29129 active+clean
>              28    active+clean+scrubbing+deep
>              2     active+clean+snaptrim
>              2     active+clean+scrubbing
>
>   io:
>     client:   484 MiB/s rd, 64 MiB/s wr, 4.64k op/s rd, 1.50k op/s wr
>
> # ceph fs status
> con-fs2 - 1554 clients
> =======
> RANK  STATE     MDS       ACTIVITY     DNS    INOS   DIRS   CAPS
>  0    active  ceph-12  Reqs:    3 /s  13.8M  13.8M   478k  29.2k
>  1    active  ceph-15  Reqs:   31 /s  10.5M  10.5M   140k   441k
>  2    active  ceph-14  Reqs:    0 /s  11.5M  11.5M   504k  32.8k
>  3    active  ceph-17  Reqs:    5 /s  12.4M  12.4M   487k  30.9k
>  4    active  ceph-08  Reqs:    0 /s  15.3M  15.3M   247k  47.2k
>  5    active  ceph-11  Reqs:    7 /s  4414k  4413k   262k  72.5k
>  6    active  ceph-16  Reqs:  409 /s  1079k  1057k  7766   17.3k
>  7    active  ceph-24  Reqs:   41 /s  4074k  4074k   448k   109k
>         POOL           TYPE     USED  AVAIL
>    con-fs2-meta1     metadata  4078G  6657G
>    con-fs2-meta2       data       0   6657G
>     con-fs2-data       data    1225T  2272T
> con-fs2-data-ec-ssd    data     794G  20.8T
>    con-fs2-data2       data    5745T  2066T
> STANDBY MDS
>   ceph-09
>   ceph-10
>   ceph-23
>   ceph-13
> MDS version: ceph version 16.2.15 (618f440892089921c3e944a991122ddc44e60516) pacific (stable)
>
> Ranks 0-4 are massively oversized. Ranks 5 and 7 show usual values. Rank 6 is low, because we restarted it already due to this warning. It seems as if MDSes don't trim cache during scrub, the sizes only increase.
>
> Is this ballooning normal or a bug? Is there a workaround apart from restarting MDSes all the time?
>
> Thanks and best regards,
> =================
> Frank Schilder
> AIT Risø Campus
> Bygning 109, rum S14
> _______________________________________________
> ceph-users mailing list -- ceph-users@xxxxxxx
> To unsubscribe send an email to ceph-users-leave@xxxxxxx



--
Alexander Patrakov
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