Re: 1 clients failing to respond to cache pressure (quincy:17.2.6)

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Every user has a 1x subvolume and I only have 1 pool.
At the beginning we were using each subvolume for ldap home directory +
user data.
When a user logins any docker on any host, it was using the cluster for
home and the for user related data, we was have second directory in the
same subvolume.
Time to time users were feeling a very slow home environment and after a
month it became almost impossible to use home. VNC sessions became
unresponsive and slow etc.

2 weeks ago, I had to migrate home to a ZFS storage and now the overall
performance is better for only user_data without home.
But still the performance is not good enough as I expected because of the
problems related to MDS.
The usage is low but allocation is high and Cpu usage is high. You saw the
IO Op/s, it's nothing but allocation is high.

I develop a fio benchmark script and I run the script on 4x test server at
the same time, the results are below:
Script:
https://github.com/ozkangoksu/benchmark/blob/8f5df87997864c25ef32447e02fcd41fda0d2a67/iobench.sh

https://github.com/ozkangoksu/benchmark/blob/main/benchmark-results/iobench-client-01.txt
https://github.com/ozkangoksu/benchmark/blob/main/benchmark-results/iobench-client-02.txt
https://github.com/ozkangoksu/benchmark/blob/main/benchmark-results/iobench-client-03.txt
https://github.com/ozkangoksu/benchmark/blob/main/benchmark-results/iobench-client-04.txt

While running benchmark, I take sample values for each type of iobench run.

Seq Write benchmarking: size=1G,direct=1,numjobs=3,iodepth=32
    client:   70 MiB/s rd, 762 MiB/s wr, 337 op/s rd, 24.41k op/s wr
    client:   60 MiB/s rd, 551 MiB/s wr, 303 op/s rd, 35.12k op/s wr
    client:   13 MiB/s rd, 161 MiB/s wr, 101 op/s rd, 41.30k op/s wr

Seq Read benchmarking: size=1G,direct=1,numjobs=3,iodepth=32
    client:   1.6 GiB/s rd, 219 KiB/s wr, 28.76k op/s rd, 89 op/s wr
    client:   370 MiB/s rd, 475 KiB/s wr, 90.38k op/s rd, 89 op/s wr

Rand Write benchmarking: size=1G,direct=1,numjobs=3,iodepth=32
    client:   63 MiB/s rd, 1.5 GiB/s wr, 8.77k op/s rd, 5.50k op/s wr
    client:   14 MiB/s rd, 1.8 GiB/s wr, 81 op/s rd, 13.86k op/s wr
    client:   6.6 MiB/s rd, 1.2 GiB/s wr, 61 op/s rd, 30.13k op/s wr

Rand Read benchmarking: size=1G,direct=1,numjobs=3,iodepth=32
    client:   317 MiB/s rd, 841 MiB/s wr, 426 op/s rd, 10.98k op/s wr
    client:   2.8 GiB/s rd, 882 MiB/s wr, 25.68k op/s rd, 291 op/s wr
    client:   4.0 GiB/s rd, 226 MiB/s wr, 89.63k op/s rd, 124 op/s wr
    client:   2.4 GiB/s rd, 295 KiB/s wr, 197.86k op/s rd, 20 op/s wr

It seems I only have problems with the 4K,8K,16K other sector sizes.




Eugen Block <eblock@xxxxxx>, 25 Oca 2024 Per, 19:06 tarihinde şunu yazdı:

> I understand that your MDS shows a high CPU usage, but other than that
> what is your performance issue? Do users complain? Do some operations
> take longer than expected? Are OSDs saturated during those phases?
> Because the cache pressure messages don’t necessarily mean that users
> will notice.
> MDS daemons are single-threaded so that might be a bottleneck. In that
> case multi-active mds might help, which you already tried and
> experienced OOM killers. But you might have to disable the mds
> balancer as someone else mentioned. And then you could think about
> pinning, is it possible to split the CephFS into multiple
> subdirectories and pin them to different ranks?
> But first I’d still like to know what the performance issue really is.
>
> Zitat von Özkan Göksu <ozkangksu@xxxxxxxxx>:
>
> > I will try my best to explain my situation.
> >
> > I don't have a separate mds server. I have 5 identical nodes, 3 of them
> > mons, and I use the other 2 as active and standby mds. (currently I have
> > left overs from max_mds 4)
> >
> > root@ud-01:~# ceph -s
> >   cluster:
> >     id:     e42fd4b0-313b-11ee-9a00-31da71873773
> >     health: HEALTH_WARN
> >             1 clients failing to respond to cache pressure
> >
> >   services:
> >     mon: 3 daemons, quorum ud-01,ud-02,ud-03 (age 9d)
> >     mgr: ud-01.qycnol(active, since 8d), standbys: ud-02.tfhqfd
> >     mds: 1/1 daemons up, 4 standby
> >     osd: 80 osds: 80 up (since 9d), 80 in (since 5M)
> >
> >   data:
> >     volumes: 1/1 healthy
> >     pools:   3 pools, 2305 pgs
> >     objects: 106.58M objects, 25 TiB
> >     usage:   45 TiB used, 101 TiB / 146 TiB avail
> >     pgs:     2303 active+clean
> >              2    active+clean+scrubbing+deep
> >
> >   io:
> >     client:   16 MiB/s rd, 3.4 MiB/s wr, 77 op/s rd, 23 op/s wr
> >
> > ------------------------------
> > root@ud-01:~# ceph fs status
> > ud-data - 84 clients
> > =======
> > RANK  STATE           MDS              ACTIVITY     DNS    INOS   DIRS
> > CAPS
> >  0    active  ud-data.ud-02.xcoojt  Reqs:   40 /s  2579k  2578k   169k
> >  3048k
> >         POOL           TYPE     USED  AVAIL
> > cephfs.ud-data.meta  metadata   136G  44.9T
> > cephfs.ud-data.data    data    44.3T  44.9T
> >
> > ------------------------------
> > root@ud-01:~# ceph health detail
> > HEALTH_WARN 1 clients failing to respond to cache pressure
> > [WRN] MDS_CLIENT_RECALL: 1 clients failing to respond to cache pressure
> >     mds.ud-data.ud-02.xcoojt(mds.0): Client bmw-m4 failing to respond to
> > cache pressure client_id: 1275577
> >
> > ------------------------------
> > When I check the failing client with session ls I see only "num_caps:
> 12298"
> >
> > ceph tell mds.ud-data.ud-02.xcoojt session ls | jq -r '.[] | "clientid:
> > \(.id)= num_caps: \(.num_caps), num_leases: \(.num_leases),
> > request_load_avg: \(.request_load_avg), num_completed_requests:
> > \(.num_completed_requests), num_completed_flushes:
> > \(.num_completed_flushes)"' | sort -n -t: -k3
> >
> > clientid: 1275577= num_caps: 12298, num_leases: 0, request_load_avg: 0,
> > num_completed_requests: 0, num_completed_flushes: 1
> > clientid: 1294542= num_caps: 13000, num_leases: 12, request_load_avg:
> 105,
> > num_completed_requests: 0, num_completed_flushes: 6
> > clientid: 1282187= num_caps: 16869, num_leases: 1, request_load_avg: 0,
> > num_completed_requests: 0, num_completed_flushes: 1
> > clientid: 1275589= num_caps: 18943, num_leases: 0, request_load_avg: 52,
> > num_completed_requests: 0, num_completed_flushes: 1
> > clientid: 1282154= num_caps: 24747, num_leases: 1, request_load_avg: 57,
> > num_completed_requests: 2, num_completed_flushes: 2
> > clientid: 1275553= num_caps: 25120, num_leases: 2, request_load_avg: 116,
> > num_completed_requests: 2, num_completed_flushes: 8
> > clientid: 1282142= num_caps: 27185, num_leases: 6, request_load_avg: 128,
> > num_completed_requests: 0, num_completed_flushes: 8
> > clientid: 1275535= num_caps: 40364, num_leases: 6, request_load_avg: 111,
> > num_completed_requests: 2, num_completed_flushes: 8
> > clientid: 1282130= num_caps: 41483, num_leases: 0, request_load_avg: 135,
> > num_completed_requests: 0, num_completed_flushes: 1
> > clientid: 1275547= num_caps: 42953, num_leases: 4, request_load_avg: 119,
> > num_completed_requests: 2, num_completed_flushes: 6
> > clientid: 1282139= num_caps: 45435, num_leases: 27, request_load_avg: 84,
> > num_completed_requests: 2, num_completed_flushes: 34
> > clientid: 1282136= num_caps: 48374, num_leases: 8, request_load_avg: 0,
> > num_completed_requests: 1, num_completed_flushes: 1
> > clientid: 1275532= num_caps: 48664, num_leases: 7, request_load_avg: 115,
> > num_completed_requests: 2, num_completed_flushes: 8
> > clientid: 1191789= num_caps: 130319, num_leases: 0, request_load_avg:
> 1753,
> > num_completed_requests: 0, num_completed_flushes: 0
> > clientid: 1275571= num_caps: 139488, num_leases: 0, request_load_avg: 2,
> > num_completed_requests: 0, num_completed_flushes: 1
> > clientid: 1282133= num_caps: 145487, num_leases: 0, request_load_avg: 8,
> > num_completed_requests: 1, num_completed_flushes: 1
> > clientid: 1534496= num_caps: 1041316, num_leases: 0, request_load_avg: 0,
> > num_completed_requests: 0, num_completed_flushes: 1
> >
> > ------------------------------
> > When I check the dashboard/service/mds I see %120+ CPU usage on active
> MDS
> > but on the host everything is almost idle and disk waits are very low.
> >
> > avg-cpu:  %user   %nice %system %iowait  %steal   %idle
> >            0.61    0.00    0.38    0.41    0.00   98.60
> >
> > Device            r/s     rMB/s   rrqm/s  %rrqm r_await rareq-sz     w/s
> >   wMB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dMB/s   drqm/s
> %drqm
> > d_await dareq-sz     f/s f_await  aqu-sz  %util
> > sdc              2.00      0.01     0.00   0.00    0.50     6.00   20.00
> >    0.04     0.00   0.00    0.50     2.00    0.00      0.00     0.00
>  0.00
> >    0.00     0.00   10.00    0.60    0.02   1.20
> > sdd              3.00      0.02     0.00   0.00    0.67     8.00  285.00
> >    1.84    77.00  21.27    0.44     6.61    0.00      0.00     0.00
>  0.00
> >    0.00     0.00  114.00    0.83    0.22  22.40
> > sde              1.00      0.01     0.00   0.00    1.00     8.00   36.00
> >    0.08     3.00   7.69    0.64     2.33    0.00      0.00     0.00
>  0.00
> >    0.00     0.00   18.00    0.67    0.04   1.60
> > sdf              5.00      0.04     0.00   0.00    0.40     7.20   40.00
> >    0.09     3.00   6.98    0.53     2.30    0.00      0.00     0.00
>  0.00
> >    0.00     0.00   20.00    0.70    0.04   2.00
> > sdg             11.00      0.08     0.00   0.00    0.73     7.27   36.00
> >    0.09     4.00  10.00    0.50     2.44    0.00      0.00     0.00
>  0.00
> >    0.00     0.00   18.00    0.72    0.04   3.20
> > sdh              5.00      0.03     0.00   0.00    0.60     5.60   46.00
> >    0.10     2.00   4.17    0.59     2.17    0.00      0.00     0.00
>  0.00
> >    0.00     0.00   23.00    0.83    0.05   2.80
> > sdi              7.00      0.04     0.00   0.00    0.43     6.29   36.00
> >    0.07     1.00   2.70    0.47     2.11    0.00      0.00     0.00
>  0.00
> >    0.00     0.00   18.00    0.61    0.03   2.40
> > sdj              5.00      0.04     0.00   0.00    0.80     7.20   42.00
> >    0.09     1.00   2.33    0.67     2.10    0.00      0.00     0.00
>  0.00
> >    0.00     0.00   21.00    0.81    0.05   3.20
> >
> > ------------------------------
> > Other than this 5x node cluster, I also have a 3x node cluster with
> > identical hardware but it serves for a different purpose and data
> workload.
> > In this cluster I don't have any problem and MDS default settings seems
> > enough.
> > The only difference between two cluster is, 5x node cluster used directly
> > by users, 3x node cluster used heavily to read and write data via
> projects
> > not by users. So allocate and de-allocate will be better.
> >
> > I guess I just have a problematic use case on the 5x node cluster and as
> I
> > mentioned above, I might have the similar problem but I don't know how to
> > debug it.
> >
> >
> https://lists.ceph.io/hyperkitty/list/ceph-users@xxxxxxx/thread/YO4SGL4DJQ6EKUBUIHKTFSW72ZJ3XLZS/
> > quote:"A user running VSCodium, keeping 15k caps open.. the opportunistic
> > caps recall eventually starts recalling those but the (el7 kernel) client
> > won't release them. Stopping Codium seems to be the only way to release."
> >
> > ------------------------------
> > Before reading the osd df you should know that I created 2x
> > OSD/per"CT4000MX500SSD1"
> > # ceph osd df tree
> > ID   CLASS  WEIGHT     REWEIGHT  SIZE     RAW USE  DATA     OMAP
> META
> >     AVAIL    %USE   VAR   PGS  STATUS  TYPE NAME
> >  -1         145.54321         -  146 TiB   45 TiB   44 TiB   119 GiB  333
> > GiB  101 TiB  30.81  1.00    -          root default
> >  -3          29.10864         -   29 TiB  8.9 TiB  8.8 TiB    25 GiB   66
> > GiB   20 TiB  30.54  0.99    -              host ud-01
> >   0    ssd    1.81929   1.00000  1.8 TiB  616 GiB  610 GiB   1.4 GiB  4.5
> > GiB  1.2 TiB  33.04  1.07   61      up          osd.0
> >   1    ssd    1.81929   1.00000  1.8 TiB  527 GiB  521 GiB   1.5 GiB  4.0
> > GiB  1.3 TiB  28.28  0.92   53      up          osd.1
> >   2    ssd    1.81929   1.00000  1.8 TiB  595 GiB  589 GiB   2.3 GiB  4.0
> > GiB  1.2 TiB  31.96  1.04   63      up          osd.2
> >   3    ssd    1.81929   1.00000  1.8 TiB  527 GiB  521 GiB   1.8 GiB  4.2
> > GiB  1.3 TiB  28.30  0.92   55      up          osd.3
> >   4    ssd    1.81929   1.00000  1.8 TiB  525 GiB  520 GiB   1.3 GiB  3.9
> > GiB  1.3 TiB  28.21  0.92   52      up          osd.4
> >   5    ssd    1.81929   1.00000  1.8 TiB  592 GiB  586 GiB   1.8 GiB  3.8
> > GiB  1.2 TiB  31.76  1.03   61      up          osd.5
> >   6    ssd    1.81929   1.00000  1.8 TiB  559 GiB  553 GiB   1.8 GiB  4.3
> > GiB  1.3 TiB  30.03  0.97   57      up          osd.6
> >   7    ssd    1.81929   1.00000  1.8 TiB  602 GiB  597 GiB   836 MiB  4.4
> > GiB  1.2 TiB  32.32  1.05   58      up          osd.7
> >   8    ssd    1.81929   1.00000  1.8 TiB  614 GiB  609 GiB   1.2 GiB  4.5
> > GiB  1.2 TiB  32.98  1.07   60      up          osd.8
> >   9    ssd    1.81929   1.00000  1.8 TiB  571 GiB  565 GiB   2.2 GiB  4.2
> > GiB  1.3 TiB  30.67  1.00   61      up          osd.9
> >  10    ssd    1.81929   1.00000  1.8 TiB  528 GiB  522 GiB   1.3 GiB  4.1
> > GiB  1.3 TiB  28.33  0.92   52      up          osd.10
> >  11    ssd    1.81929   1.00000  1.8 TiB  551 GiB  546 GiB   1.5 GiB  3.6
> > GiB  1.3 TiB  29.57  0.96   56      up          osd.11
> >  12    ssd    1.81929   1.00000  1.8 TiB  594 GiB  588 GiB   1.8 GiB  4.4
> > GiB  1.2 TiB  31.91  1.04   61      up          osd.12
> >  13    ssd    1.81929   1.00000  1.8 TiB  561 GiB  555 GiB   1.1 GiB  4.3
> > GiB  1.3 TiB  30.10  0.98   55      up          osd.13
> >  14    ssd    1.81929   1.00000  1.8 TiB  616 GiB  609 GiB   1.9 GiB  4.2
> > GiB  1.2 TiB  33.04  1.07   64      up          osd.14
> >  15    ssd    1.81929   1.00000  1.8 TiB  525 GiB  520 GiB   1.1 GiB  4.0
> > GiB  1.3 TiB  28.20  0.92   51      up          osd.15
> >  -5          29.10864         -   29 TiB  9.0 TiB  8.9 TiB    22 GiB   67
> > GiB   20 TiB  30.89  1.00    -              host ud-02
> >  16    ssd    1.81929   1.00000  1.8 TiB  617 GiB  611 GiB   1.7 GiB  4.7
> > GiB  1.2 TiB  33.12  1.08   63      up          osd.16
> >  17    ssd    1.81929   1.00000  1.8 TiB  582 GiB  577 GiB   1.6 GiB  4.0
> > GiB  1.3 TiB  31.26  1.01   59      up          osd.17
> >  18    ssd    1.81929   1.00000  1.8 TiB  583 GiB  578 GiB   418 MiB  4.0
> > GiB  1.3 TiB  31.29  1.02   54      up          osd.18
> >  19    ssd    1.81929   1.00000  1.8 TiB  550 GiB  544 GiB   1.5 GiB  4.0
> > GiB  1.3 TiB  29.50  0.96   56      up          osd.19
> >  20    ssd    1.81929   1.00000  1.8 TiB  551 GiB  546 GiB   1.1 GiB  4.1
> > GiB  1.3 TiB  29.57  0.96   54      up          osd.20
> >  21    ssd    1.81929   1.00000  1.8 TiB  616 GiB  610 GiB   1.3 GiB  4.4
> > GiB  1.2 TiB  33.04  1.07   60      up          osd.21
> >  22    ssd    1.81929   1.00000  1.8 TiB  573 GiB  567 GiB   1.6 GiB  4.1
> > GiB  1.3 TiB  30.75  1.00   58      up          osd.22
> >  23    ssd    1.81929   1.00000  1.8 TiB  616 GiB  610 GiB   1.3 GiB  4.3
> > GiB  1.2 TiB  33.06  1.07   60      up          osd.23
> >  24    ssd    1.81929   1.00000  1.8 TiB  539 GiB  534 GiB   844 MiB  3.8
> > GiB  1.3 TiB  28.92  0.94   51      up          osd.24
> >  25    ssd    1.81929   1.00000  1.8 TiB  583 GiB  576 GiB   2.1 GiB  4.1
> > GiB  1.3 TiB  31.27  1.02   61      up          osd.25
> >  26    ssd    1.81929   1.00000  1.8 TiB  617 GiB  611 GiB   1.3 GiB  4.6
> > GiB  1.2 TiB  33.12  1.08   61      up          osd.26
> >  27    ssd    1.81929   1.00000  1.8 TiB  537 GiB  532 GiB   1.2 GiB  4.1
> > GiB  1.3 TiB  28.84  0.94   53      up          osd.27
> >  28    ssd    1.81929   1.00000  1.8 TiB  527 GiB  522 GiB   1.3 GiB  4.2
> > GiB  1.3 TiB  28.29  0.92   53      up          osd.28
> >  29    ssd    1.81929   1.00000  1.8 TiB  594 GiB  588 GiB   1.5 GiB  4.6
> > GiB  1.2 TiB  31.91  1.04   59      up          osd.29
> >  30    ssd    1.81929   1.00000  1.8 TiB  528 GiB  523 GiB   1.4 GiB  4.1
> > GiB  1.3 TiB  28.35  0.92   53      up          osd.30
> >  31    ssd    1.81929   1.00000  1.8 TiB  594 GiB  589 GiB   1.6 GiB  3.8
> > GiB  1.2 TiB  31.89  1.03   61      up          osd.31
> >  -7          29.10864         -   29 TiB  8.9 TiB  8.8 TiB    23 GiB   67
> > GiB   20 TiB  30.66  1.00    -              host ud-03
> >  32    ssd    1.81929   1.00000  1.8 TiB  593 GiB  588 GiB   1.1 GiB  4.3
> > GiB  1.2 TiB  31.84  1.03   57      up          osd.32
> >  33    ssd    1.81929   1.00000  1.8 TiB  617 GiB  611 GiB   1.8 GiB  4.4
> > GiB  1.2 TiB  33.13  1.08   63      up          osd.33
> >  34    ssd    1.81929   1.00000  1.8 TiB  537 GiB  532 GiB   2.0 GiB  3.8
> > GiB  1.3 TiB  28.84  0.94   59      up          osd.34
> >  35    ssd    1.81929   1.00000  1.8 TiB  562 GiB  556 GiB   1.7 GiB  4.2
> > GiB  1.3 TiB  30.16  0.98   58      up          osd.35
> >  36    ssd    1.81929   1.00000  1.8 TiB  529 GiB  523 GiB   1.3 GiB  3.9
> > GiB  1.3 TiB  28.38  0.92   52      up          osd.36
> >  37    ssd    1.81929   1.00000  1.8 TiB  527 GiB  521 GiB   1.7 GiB  4.2
> > GiB  1.3 TiB  28.28  0.92   55      up          osd.37
> >  38    ssd    1.81929   1.00000  1.8 TiB  574 GiB  568 GiB   1.2 GiB  4.3
> > GiB  1.3 TiB  30.79  1.00   55      up          osd.38
> >  39    ssd    1.81929   1.00000  1.8 TiB  605 GiB  599 GiB   1.6 GiB  4.2
> > GiB  1.2 TiB  32.48  1.05   61      up          osd.39
> >  40    ssd    1.81929   1.00000  1.8 TiB  573 GiB  567 GiB   1.2 GiB  4.4
> > GiB  1.3 TiB  30.76  1.00   56      up          osd.40
> >  41    ssd    1.81929   1.00000  1.8 TiB  526 GiB  520 GiB   1.7 GiB  3.9
> > GiB  1.3 TiB  28.21  0.92   54      up          osd.41
> >  42    ssd    1.81929   1.00000  1.8 TiB  613 GiB  608 GiB  1010 MiB  4.4
> > GiB  1.2 TiB  32.91  1.07   58      up          osd.42
> >  43    ssd    1.81929   1.00000  1.8 TiB  606 GiB  600 GiB   1.7 GiB  4.3
> > GiB  1.2 TiB  32.51  1.06   61      up          osd.43
> >  44    ssd    1.81929   1.00000  1.8 TiB  583 GiB  577 GiB   1.6 GiB  4.2
> > GiB  1.3 TiB  31.29  1.02   60      up          osd.44
> >  45    ssd    1.81929   1.00000  1.8 TiB  618 GiB  613 GiB   1.4 GiB  4.3
> > GiB  1.2 TiB  33.18  1.08   62      up          osd.45
> >  46    ssd    1.81929   1.00000  1.8 TiB  550 GiB  544 GiB   1.5 GiB  4.2
> > GiB  1.3 TiB  29.50  0.96   54      up          osd.46
> >  47    ssd    1.81929   1.00000  1.8 TiB  526 GiB  522 GiB   692 MiB  3.7
> > GiB  1.3 TiB  28.25  0.92   50      up          osd.47
> >  -9          29.10864         -   29 TiB  9.0 TiB  8.9 TiB    26 GiB   68
> > GiB   20 TiB  31.04  1.01    -              host ud-04
> >  48    ssd    1.81929   1.00000  1.8 TiB  540 GiB  534 GiB   2.2 GiB  3.6
> > GiB  1.3 TiB  28.96  0.94   58      up          osd.48
> >  49    ssd    1.81929   1.00000  1.8 TiB  617 GiB  611 GiB   1.4 GiB  4.5
> > GiB  1.2 TiB  33.11  1.07   61      up          osd.49
> >  50    ssd    1.81929   1.00000  1.8 TiB  618 GiB  612 GiB   1.2 GiB  4.8
> > GiB  1.2 TiB  33.17  1.08   61      up          osd.50
> >  51    ssd    1.81929   1.00000  1.8 TiB  618 GiB  612 GiB   1.5 GiB  4.5
> > GiB  1.2 TiB  33.19  1.08   61      up          osd.51
> >  52    ssd    1.81929   1.00000  1.8 TiB  526 GiB  521 GiB   1.4 GiB  4.1
> > GiB  1.3 TiB  28.25  0.92   53      up          osd.52
> >  53    ssd    1.81929   1.00000  1.8 TiB  618 GiB  611 GiB   2.4 GiB  4.3
> > GiB  1.2 TiB  33.17  1.08   66      up          osd.53
> >  54    ssd    1.81929   1.00000  1.8 TiB  550 GiB  544 GiB   1.5 GiB  4.3
> > GiB  1.3 TiB  29.54  0.96   55      up          osd.54
> >  55    ssd    1.81929   1.00000  1.8 TiB  527 GiB  522 GiB   1.3 GiB  4.0
> > GiB  1.3 TiB  28.29  0.92   52      up          osd.55
> >  56    ssd    1.81929   1.00000  1.8 TiB  525 GiB  519 GiB   1.2 GiB  4.1
> > GiB  1.3 TiB  28.16  0.91   52      up          osd.56
> >  57    ssd    1.81929   1.00000  1.8 TiB  615 GiB  609 GiB   2.3 GiB  4.2
> > GiB  1.2 TiB  33.03  1.07   65      up          osd.57
> >  58    ssd    1.81929   1.00000  1.8 TiB  527 GiB  522 GiB   1.6 GiB  3.7
> > GiB  1.3 TiB  28.31  0.92   55      up          osd.58
> >  59    ssd    1.81929   1.00000  1.8 TiB  615 GiB  609 GiB   1.2 GiB  4.6
> > GiB  1.2 TiB  33.01  1.07   60      up          osd.59
> >  60    ssd    1.81929   1.00000  1.8 TiB  594 GiB  588 GiB   1.2 GiB  4.4
> > GiB  1.2 TiB  31.88  1.03   59      up          osd.60
> >  61    ssd    1.81929   1.00000  1.8 TiB  616 GiB  610 GiB   1.9 GiB  4.1
> > GiB  1.2 TiB  33.04  1.07   64      up          osd.61
> >  62    ssd    1.81929   1.00000  1.8 TiB  620 GiB  614 GiB   1.9 GiB  4.4
> > GiB  1.2 TiB  33.27  1.08   63      up          osd.62
> >  63    ssd    1.81929   1.00000  1.8 TiB  527 GiB  522 GiB   1.5 GiB  4.0
> > GiB  1.3 TiB  28.30  0.92   53      up          osd.63
> > -11          29.10864         -   29 TiB  9.0 TiB  8.9 TiB    23 GiB   65
> > GiB   20 TiB  30.91  1.00    -              host ud-05
> >  64    ssd    1.81929   1.00000  1.8 TiB  608 GiB  601 GiB   2.3 GiB  4.5
> > GiB  1.2 TiB  32.62  1.06   65      up          osd.64
> >  65    ssd    1.81929   1.00000  1.8 TiB  606 GiB  601 GiB   628 MiB  4.2
> > GiB  1.2 TiB  32.53  1.06   57      up          osd.65
> >  66    ssd    1.81929   1.00000  1.8 TiB  583 GiB  578 GiB   1.3 GiB  4.3
> > GiB  1.2 TiB  31.31  1.02   57      up          osd.66
> >  67    ssd    1.81929   1.00000  1.8 TiB  537 GiB  533 GiB   436 MiB  3.6
> > GiB  1.3 TiB  28.82  0.94   50      up          osd.67
> >  68    ssd    1.81929   1.00000  1.8 TiB  541 GiB  535 GiB   2.5 GiB  3.8
> > GiB  1.3 TiB  29.04  0.94   59      up          osd.68
> >  69    ssd    1.81929   1.00000  1.8 TiB  606 GiB  601 GiB   1.1 GiB  4.4
> > GiB  1.2 TiB  32.55  1.06   59      up          osd.69
> >  70    ssd    1.81929   1.00000  1.8 TiB  604 GiB  598 GiB   1.8 GiB  4.1
> > GiB  1.2 TiB  32.44  1.05   63      up          osd.70
> >  71    ssd    1.81929   1.00000  1.8 TiB  606 GiB  600 GiB   1.9 GiB  4.5
> > GiB  1.2 TiB  32.53  1.06   62      up          osd.71
> >  72    ssd    1.81929   1.00000  1.8 TiB  602 GiB  598 GiB   612 MiB  4.1
> > GiB  1.2 TiB  32.33  1.05   57      up          osd.72
> >  73    ssd    1.81929   1.00000  1.8 TiB  571 GiB  565 GiB   1.8 GiB  4.5
> > GiB  1.3 TiB  30.65  0.99   58      up          osd.73
> >  74    ssd    1.81929   1.00000  1.8 TiB  608 GiB  602 GiB   1.8 GiB  4.2
> > GiB  1.2 TiB  32.62  1.06   61      up          osd.74
> >  75    ssd    1.81929   1.00000  1.8 TiB  536 GiB  531 GiB   1.9 GiB  3.5
> > GiB  1.3 TiB  28.80  0.93   57      up          osd.75
> >  76    ssd    1.81929   1.00000  1.8 TiB  605 GiB  599 GiB   1.4 GiB  4.5
> > GiB  1.2 TiB  32.48  1.05   60      up          osd.76
> >  77    ssd    1.81929   1.00000  1.8 TiB  537 GiB  532 GiB   1.2 GiB  3.9
> > GiB  1.3 TiB  28.84  0.94   52      up          osd.77
> >  78    ssd    1.81929   1.00000  1.8 TiB  525 GiB  520 GiB   1.3 GiB  3.8
> > GiB  1.3 TiB  28.20  0.92   52      up          osd.78
> >  79    ssd    1.81929   1.00000  1.8 TiB  536 GiB  531 GiB   1.1 GiB  3.3
> > GiB  1.3 TiB  28.76  0.93   53      up          osd.79
> >                           TOTAL  146 TiB   45 TiB   44 TiB   119 GiB  333
> > GiB  101 TiB  30.81
> > MIN/MAX VAR: 0.91/1.08  STDDEV: 1.90
> >
> >
> >
> > Eugen Block <eblock@xxxxxx>, 25 Oca 2024 Per, 16:52 tarihinde şunu
> yazdı:
> >
> >> There is no definitive answer wrt mds tuning. As it is everywhere
> >> mentioned, it's about finding the right setup for your specific
> >> workload. If you can synthesize your workload (maybe scale down a bit)
> >> try optimizing it in a test cluster without interrupting your
> >> developers too much.
> >> But what you haven't explained yet is what are you experiencing as a
> >> performance issue? Do you have numbers or a detailed description?
> >>  From the fs status output you didn't seem to have too much activity
> >> going on (around 140 requests per second), but that's probably not the
> >> usual traffic? What does ceph report in its client IO output?
> >> Can you paste the 'ceph osd df' output as well?
> >> Do you have dedicated MDS servers or are they colocated with other
> >> services?
> >>
> >> Zitat von Özkan Göksu <ozkangksu@xxxxxxxxx>:
> >>
> >> > Hello  Eugen.
> >> >
> >> > I read all of your MDS related topics and thank you so much for your
> >> effort
> >> > on this.
> >> > There is not much information and I couldn't find a MDS tuning guide
> at
> >> > all. It  seems that you are the correct person to discuss mds
> debugging
> >> and
> >> > tuning.
> >> >
> >> > Do you have any documents or may I learn what is the proper way to
> debug
> >> > MDS and clients ?
> >> > Which debug logs will guide me to understand the limitations and will
> >> help
> >> > to tune according to the data flow?
> >> >
> >> > While searching, I find this:
> >> >
> >>
> https://lists.ceph.io/hyperkitty/list/ceph-users@xxxxxxx/thread/YO4SGL4DJQ6EKUBUIHKTFSW72ZJ3XLZS/
> >> > quote:"A user running VSCodium, keeping 15k caps open.. the
> opportunistic
> >> > caps recall eventually starts recalling those but the (el7 kernel)
> client
> >> > won't release them. Stopping Codium seems to be the only way to
> release."
> >> >
> >> > Because of this I think I also need to play around with the client
> side
> >> too.
> >> >
> >> > My main goal is increasing the speed and reducing the latency and I
> >> wonder
> >> > if these ideas are correct or not:
> >> > - Maybe I need to increase client side cache size because via each
> >> client,
> >> > multiple users request a lot of objects and clearly the
> >> > client_cache_size=16 default is not enough.
> >> > -  Maybe I need to increase client side maximum cache limit for
> >> > object "client_oc_max_objects=1000 to 10000" and data
> >> "client_oc_size=200mi
> >> > to 400mi"
> >> > - The client cache cleaning threshold is not aggressive enough to keep
> >> the
> >> > free cache size in the desired range. I need to make it aggressive but
> >> this
> >> > should not reduce speed and increase latency.
> >> >
> >> > mds_cache_memory_limit=4gi to 16gi
> >> > client_oc_max_objects=1000 to 10000
> >> > client_oc_size=200mi to 400mi
> >> > client_permissions=false #to reduce latency.
> >> > client_cache_size=16 to 128
> >> >
> >> >
> >> > What do you think?
> >>
> >>
> >>
> >>
>
>
>
>
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