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?
