Sorry, this will be a long email with everything I find to be relevant.
I have a mdraid6 array with 36 hdd SAS drives each able to do
>200MB/s, but I am unable to get more than 38MB/s resync speed on a
fast system (48cores/96GB ram) with no other load.
Here are all details:
kernel 5.13.11-1.el8.elrepo.x86_64
# mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Tue Aug 17 09:37:39 2021
Raid Level : raid6
Array Size : 464838634496 (432.91 TiB 475.99 TB)
Used Dev Size : 13671724544 (12.73 TiB 14.00 TB)
Raid Devices : 36
Total Devices : 36
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Thu Aug 19 09:26:33 2021
State : clean, resyncing
Active Devices : 36
Working Devices : 36
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Consistency Policy : bitmap
Resync Status : 49% complete
Name : large1:0 (local to host large1)
UUID : b7cace22:832e570f:eba39768:bb1a1ed6
Events : 40702
Number Major Minor RaidDevice State
0 8 33 0 active sync /dev/sdc1
1 8 49 1 active sync /dev/sdd1
2 8 65 2 active sync /dev/sde1
3 8 81 3 active sync /dev/sdf1
4 8 97 4 active sync /dev/sdg1
5 8 113 5 active sync /dev/sdh1
6 8 129 6 active sync /dev/sdi1
7 8 145 7 active sync /dev/sdj1
8 8 161 8 active sync /dev/sdk1
9 8 209 9 active sync /dev/sdn1
10 8 177 10 active sync /dev/sdl1
11 8 225 11 active sync /dev/sdo1
12 8 241 12 active sync /dev/sdp1
13 65 1 13 active sync /dev/sdq1
14 65 17 14 active sync /dev/sdr1
15 8 193 15 active sync /dev/sdm1
16 65 145 16 active sync /dev/sdz1
17 65 161 17 active sync /dev/sdaa1
18 65 33 18 active sync /dev/sds1
19 65 49 19 active sync /dev/sdt1
20 65 65 20 active sync /dev/sdu1
21 65 81 21 active sync /dev/sdv1
22 65 97 22 active sync /dev/sdw1
23 65 113 23 active sync /dev/sdx1
24 65 129 24 active sync /dev/sdy1
25 65 177 25 active sync /dev/sdab1
26 65 193 26 active sync /dev/sdac1
27 65 209 27 active sync /dev/sdad1
28 65 225 28 active sync /dev/sdae1
29 65 241 29 active sync /dev/sdaf1
30 66 1 30 active sync /dev/sdag1
31 66 17 31 active sync /dev/sdah1
32 66 33 32 active sync /dev/sdai1
33 66 49 33 active sync /dev/sdaj1
34 66 65 34 active sync /dev/sdak1
35 66 81 35 active sync /dev/sdal1
# cat /proc/mdstat
md0 : active raid6 sdal1[35] sdak1[34] sdaj1[33] sdah1[31] sdai1[32]
sdag1[30] sdaf1[29] sdac1[26] sdae1[28] sdab1[25] sdad1[27] sds1[18]
sdq1[13] sdz1[16] sdo1[11] sdp1[12] sdx1[23] sdr1[14] sdw1[22] sdn1[9]
sdaa1[17] sdv1[21] sdu1[20] sdy1[24] sdt1[19] sdk1[8] sdm1[15]
sdl1[10] sdh1[5] sdj1[7] sdf1[3] sdi1[6] sdc1[0] sdg1[4] sde1[2]
sdd1[1]
464838634496 blocks super 1.2 level 6, 512k chunk, algorithm 2
[36/36] [UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU]
[=========>...........] resync = 49.5% (6773640400/13671724544)
finish=3026.3min speed=37987K/sec
bitmap: 53/102 pages [212KB], 65536KB chunk
# iostat -dx 5
Device r/s w/s rkB/s wkB/s rrqm/s wrqm/s
%rrqm %wrqm r_await w_await aqu-sz rareq-sz wareq-sz svctm %util
sdc 9738.60 1.40 38956.00 5.80 0.40 0.40
0.00 22.22 0.20 9.29 1.93 4.00 4.14 0.07 71.82
sdd 9738.20 1.00 38952.80 2.60 0.00 0.00
0.00 0.00 0.89 5.80 8.68 4.00 2.60 0.07 71.60
sde 9738.60 1.40 38956.00 5.80 0.40 0.40
0.00 22.22 0.31 3.71 3.02 4.00 4.14 0.07 70.60
sdf 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.17 3.20 1.69 4.00 2.60 0.07 70.56
sdg 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.85 4.20 8.31 4.00 2.60 0.07 70.72
sdh 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.20 4.00 1.93 4.00 2.60 0.07 70.64
sdi 9738.60 1.00 38954.40 2.60 0.00 0.00
0.00 0.00 0.17 8.20 1.70 4.00 2.60 0.07 70.98
sdj 9714.60 1.00 38954.40 2.60 24.00 0.00
0.25 0.00 0.58 4.00 5.61 4.01 2.60 0.07 70.66
sdk 9677.00 1.00 38953.60 2.60 61.40 0.00
0.63 0.00 1.23 4.40 11.94 4.03 2.60 0.07 70.76
sdl 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.15 5.80 1.44 4.00 2.60 0.07 70.76
sdm 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.38 2.80 3.73 4.00 2.60 0.07 70.96
sdo 9705.60 1.00 38953.60 2.60 32.80 0.00
0.34 0.00 0.83 5.80 8.07 4.01 2.60 0.07 70.80
sdp 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.30 4.20 2.91 4.00 2.60 0.07 70.60
sdn 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.34 5.60 3.30 4.00 2.60 0.07 70.76
sdt 9659.80 1.00 38954.40 2.60 78.80 0.00
0.81 0.00 1.00 4.00 9.71 4.03 2.60 0.07 70.44
sds 9640.40 1.00 38954.40 2.60 98.20 0.00
1.01 0.00 1.29 5.60 12.42 4.04 2.60 0.07 70.60
sdq 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.30 4.40 2.92 4.00 2.60 0.07 70.68
sdu 9738.60 1.00 38954.40 2.60 0.00 0.00
0.00 0.00 0.13 4.40 1.31 4.00 2.60 0.07 70.66
sdv 9696.20 1.00 38954.40 2.60 42.40 0.00
0.44 0.00 1.30 4.20 12.57 4.02 2.60 0.07 70.76
sdw 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.94 4.20 9.13 4.00 2.60 0.07 70.70
sdy 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.11 4.40 1.05 4.00 2.60 0.07 70.62
sdr 9730.80 1.00 38953.60 2.60 7.60 0.00
0.08 0.00 1.22 4.20 11.87 4.00 2.60 0.07 70.68
sdx 9718.00 1.00 38954.40 2.60 20.60 0.00
0.21 0.00 0.88 4.20 8.57 4.01 2.60 0.07 70.70
sdaa 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.24 4.20 2.38 4.00 2.60 0.07 70.60
sdz 9738.40 1.00 38953.60 2.60 0.00 0.00
0.00 0.00 0.20 4.20 1.91 4.00 2.60 0.07 70.60
sdab 9633.60 1.00 38953.60 2.60 104.80 0.00
1.08 0.00 1.38 4.20 13.33 4.04 2.60 0.07 70.52
sdac 9639.20 1.00 38954.40 2.60 99.40 0.00
1.02 0.00 1.08 5.60 10.45 4.04 2.60 0.07 70.56
sdad 9536.20 1.00 38954.40 2.60 202.40 0.00
2.08 0.00 2.73 4.00 26.04 4.08 2.60 0.07 70.36
sdaf 9738.60 1.00 38954.40 2.60 0.00 0.00
0.00 0.00 0.37 4.00 3.63 4.00 2.60 0.07 70.64
sdae 9738.60 1.00 38954.40 2.60 0.00 0.00
0.00 0.00 0.16 5.40 1.61 4.00 2.60 0.07 70.72
sdag 9735.20 1.00 38940.80 2.60 0.00 0.00
0.00 0.00 0.46 5.80 4.48 4.00 2.60 0.07 70.76
sdai 9738.60 1.00 38954.40 2.60 0.00 0.00
0.00 0.00 0.31 4.00 3.01 4.00 2.60 0.07 70.60
sdah 9661.60 1.00 38955.20 2.60 77.00 0.00
0.79 0.00 1.51 4.20 14.57 4.03 2.60 0.07 70.70
sdal 9739.20 1.40 38958.40 5.80 0.40 0.40
0.00 22.22 0.27 4.86 2.65 4.00 4.14 0.07 70.80
sdaj 9738.60 1.00 38954.40 2.60 0.00 0.00
0.00 0.00 0.17 4.40 1.68 4.00 2.60 0.07 70.64
sdak 9738.80 1.00 38955.20 2.60 0.00 0.00
0.00 0.00 0.53 5.40 5.21 4.00 2.60 0.07 70.80
# blockdev --report
RO RA SSZ BSZ StartSec Size Device
rw 8192 512 4096 0 480103981056 /dev/sda
rw 8192 512 4096 2048 535822336 /dev/sda1
rw 8192 512 4096 1048576 536870912 /dev/sda2
rw 8192 512 4096 2097152 447569985536 /dev/sda3
rw 8192 512 4096 876257280 31457280000 /dev/sda4
rw 8192 512 4096 0 480103981056 /dev/sdb
rw 8192 512 512 2048 535822336 /dev/sdb1
rw 8192 512 4096 1048576 536870912 /dev/sdb2
rw 8192 512 4096 2097152 447569985536 /dev/sdb3
rw 8192 512 4096 876257280 31457280000 /dev/sdb4
rw 8192 512 512 937698992 2080256 /dev/sdb5
rw 8192 512 4096 0 14000519643136 /dev/sdc
rw 8192 512 512 2048 13999981706752 /dev/sdc1
rw 8192 512 4096 0 14000519643136 /dev/sdd
rw 8192 512 512 2048 13999981706752 /dev/sdd1
rw 8192 512 4096 0 14000519643136 /dev/sde
rw 8192 512 512 2048 13999981706752 /dev/sde1
rw 8192 512 4096 0 14000519643136 /dev/sdf
rw 8192 512 512 2048 13999981706752 /dev/sdf1
rw 8192 512 4096 0 14000519643136 /dev/sdg
rw 8192 512 512 2048 13999981706752 /dev/sdg1
rw 8192 512 4096 0 14000519643136 /dev/sdh
rw 8192 512 512 2048 13999981706752 /dev/sdh1
rw 8192 512 4096 0 14000519643136 /dev/sdi
rw 8192 512 512 2048 13999981706752 /dev/sdi1
rw 8192 512 4096 0 14000519643136 /dev/sdj
rw 8192 512 512 2048 13999981706752 /dev/sdj1
rw 8192 512 4096 0 536281088 /dev/md2
rw 8192 512 4096 0 14000519643136 /dev/sdk
rw 8192 512 512 2048 13999981706752 /dev/sdk1
rw 8192 512 4096 0 14000519643136 /dev/sdl
rw 8192 512 512 2048 13999981706752 /dev/sdl1
rw 8192 512 4096 0 447435767808 /dev/md3
rw 8192 512 4096 0 14000519643136 /dev/sdm
rw 8192 512 512 2048 13999981706752 /dev/sdm1
rw 69632 512 4096 0 475994761723904 /dev/md0
rw 8192 512 4096 0 14000519643136 /dev/sdo
rw 8192 512 512 2048 13999981706752 /dev/sdo1
rw 8192 512 4096 0 14000519643136 /dev/sdp
rw 8192 512 512 2048 13999981706752 /dev/sdp1
rw 8192 512 4096 0 14000519643136 /dev/sdn
rw 8192 512 512 2048 13999981706752 /dev/sdn1
rw 8192 512 4096 0 14000519643136 /dev/sdt
rw 8192 512 512 2048 13999981706752 /dev/sdt1
rw 8192 512 4096 0 14000519643136 /dev/sds
rw 8192 512 512 2048 13999981706752 /dev/sds1
rw 8192 512 4096 0 14000519643136 /dev/sdq
rw 8192 512 512 2048 13999981706752 /dev/sdq1
rw 8192 512 4096 0 14000519643136 /dev/sdu
rw 8192 512 512 2048 13999981706752 /dev/sdu1
rw 8192 512 4096 0 14000519643136 /dev/sdv
rw 8192 512 512 2048 13999981706752 /dev/sdv1
rw 8192 512 4096 0 14000519643136 /dev/sdw
rw 8192 512 512 2048 13999981706752 /dev/sdw1
rw 8192 512 4096 0 14000519643136 /dev/sdy
rw 8192 512 512 2048 13999981706752 /dev/sdy1
rw 8192 512 4096 0 14000519643136 /dev/sdr
rw 8192 512 512 2048 13999981706752 /dev/sdr1
rw 8192 512 4096 0 14000519643136 /dev/sdx
rw 8192 512 512 2048 13999981706752 /dev/sdx1
rw 8192 512 4096 0 14000519643136 /dev/sdaa
rw 8192 512 512 2048 13999981706752 /dev/sdaa1
rw 8192 512 4096 0 14000519643136 /dev/sdz
rw 8192 512 512 2048 13999981706752 /dev/sdz1
rw 8192 512 4096 0 14000519643136 /dev/sdab
rw 8192 512 512 2048 13999981706752 /dev/sdab1
rw 8192 512 4096 0 14000519643136 /dev/sdac
rw 8192 512 512 2048 13999981706752 /dev/sdac1
rw 8192 512 4096 0 14000519643136 /dev/sdad
rw 8192 512 512 2048 13999981706752 /dev/sdad1
rw 8192 512 4096 0 14000519643136 /dev/sdaf
rw 8192 512 512 2048 13999981706752 /dev/sdaf1
rw 8192 512 4096 0 14000519643136 /dev/sdae
rw 8192 512 512 2048 13999981706752 /dev/sdae1
rw 8192 512 4096 0 14000519643136 /dev/sdag
rw 8192 512 512 2048 13999981706752 /dev/sdag1
rw 8192 512 4096 0 14000519643136 /dev/sdai
rw 8192 512 512 2048 13999981706752 /dev/sdai1
rw 8192 512 4096 0 14000519643136 /dev/sdah
rw 8192 512 512 2048 13999981706752 /dev/sdah1
rw 8192 512 4096 0 14000519643136 /dev/sdal
rw 8192 512 512 2048 13999981706752 /dev/sdal1
rw 8192 512 4096 0 14000519643136 /dev/sdaj
rw 8192 512 512 2048 13999981706752 /dev/sdaj1
rw 8192 512 4096 0 14000519643136 /dev/sdak
rw 8192 512 512 2048 13999981706752 /dev/sdak1
# find /sys/block/md0/queue/ -type f -printf "%h/%f : " -exec cat '{}' ';'
/sys/block/md0/queue/io_poll_delay : 0
/sys/block/md0/queue/max_integrity_segments : 0
/sys/block/md0/queue/zoned : none
/sys/block/md0/queue/scheduler : none
/sys/block/md0/queue/io_poll : 0
/sys/block/md0/queue/discard_zeroes_data : 0
/sys/block/md0/queue/minimum_io_size : 524288
/sys/block/md0/queue/nr_zones : 0
/sys/block/md0/queue/write_same_max_bytes : 0
/sys/block/md0/queue/max_segments : 128
/sys/block/md0/queue/dax : 0
/sys/block/md0/queue/physical_block_size : 4096
/sys/block/md0/queue/logical_block_size : 512
/sys/block/md0/queue/virt_boundary_mask : 0
/sys/block/md0/queue/zone_append_max_bytes : 0
/sys/block/md0/queue/nr_requests : 128
/sys/block/md0/queue/write_cache : write back
/sys/block/md0/queue/stable_writes : 0
/sys/block/md0/queue/max_segment_size : 4294967295
/sys/block/md0/queue/rotational : 1
/sys/block/md0/queue/discard_max_bytes : 0
/sys/block/md0/queue/add_random : 0
/sys/block/md0/queue/discard_max_hw_bytes : 0
/sys/block/md0/queue/optimal_io_size : 17825792
/sys/block/md0/queue/chunk_sectors : 0
/sys/block/md0/queue/read_ahead_kb : 34816
/sys/block/md0/queue/max_discard_segments : 1
/sys/block/md0/queue/write_zeroes_max_bytes : 0
/sys/block/md0/queue/nomerges : 0
/sys/block/md0/queue/zone_write_granularity : 0
/sys/block/md0/queue/wbt_lat_usec : cat:
/sys/block/md0/queue/wbt_lat_usec: Invalid argument
/sys/block/md0/queue/fua : 1
/sys/block/md0/queue/discard_granularity : 33554432
/sys/block/md0/queue/rq_affinity : 0
/sys/block/md0/queue/max_sectors_kb : 1280
/sys/block/md0/queue/hw_sector_size : 512
/sys/block/md0/queue/max_hw_sectors_kb : 2147483647
/sys/block/md0/queue/iostats : 0
# find /sys/block/md0/md/ -type f -not -path "*/dev-*" -printf "%h/%f
: " -exec cat '{}' ';'
/sys/block/md0/md/sync_min : 0
/sys/block/md0/md/new_dev : cat: /sys/block/md0/md/new_dev: Permission denied
/sys/block/md0/md/consistency_policy : bitmap
/sys/block/md0/md/sync_max : max
/sys/block/md0/md/sync_speed_min : 1000 (local)
/sys/block/md0/md/stripe_cache_active : 37522
/sys/block/md0/md/stripe_cache_size : 32768
/sys/block/md0/md/array_size : default
/sys/block/md0/md/suspend_hi : 0
/sys/block/md0/md/chunk_size : 524288
/sys/block/md0/md/max_read_errors : 20
/sys/block/md0/md/component_size : 13671724544
/sys/block/md0/md/rmw_level : 1
/sys/block/md0/md/sync_speed_max : 200000 (system)
/sys/block/md0/md/sync_force_parallel : 0
/sys/block/md0/md/layout : 2
/sys/block/md0/md/safe_mode_delay : 0.201
/sys/block/md0/md/reshape_position : none
/sys/block/md0/md/sync_action : resync
/sys/block/md0/md/resync_start : 13501066048
/sys/block/md0/md/serialize_policy : n/a
/sys/block/md0/md/bitmap_set_bits : cat:
/sys/block/md0/md/bitmap_set_bits: Permission denied
/sys/block/md0/md/degraded : 0
/sys/block/md0/md/bitmap/location : +8
/sys/block/md0/md/bitmap/space : 0
/sys/block/md0/md/bitmap/can_clear : false
/sys/block/md0/md/bitmap/metadata : internal
/sys/block/md0/md/bitmap/max_backlog_used : 0
/sys/block/md0/md/bitmap/time_base : 5
/sys/block/md0/md/bitmap/chunksize : 67108864
/sys/block/md0/md/bitmap/backlog : 0
/sys/block/md0/md/uuid : b7cace22-832e-570f-eba3-9768bb1a1ed6
/sys/block/md0/md/skip_copy : 0
/sys/block/md0/md/mismatch_cnt : 0
/sys/block/md0/md/last_sync_action : resync
/sys/block/md0/md/sync_speed : 38966
/sys/block/md0/md/raid_disks : 36
/sys/block/md0/md/sync_completed : 13518742200 / 27343449088
/sys/block/md0/md/array_state : active-idle
/sys/block/md0/md/reshape_direction : forwards
/sys/block/md0/md/journal_mode : /sys/block/md0/md/level : raid6
/sys/block/md0/md/suspend_lo : 0
/sys/block/md0/md/fail_last_dev : 0
/sys/block/md0/md/preread_bypass_threshold : 1
/sys/block/md0/md/stripe_size : 4096
/sys/block/md0/md/group_thread_cnt : 0
/sys/block/md0/md/metadata_version : 1.2
/sys/block/md0/md/ppl_write_hint : 0
# find /sys/block/sdc/queue/ -type f -printf "%h/%f : " -exec cat '{}' ';'
/sys/block/sdc/queue/io_poll_delay : -1
/sys/block/sdc/queue/max_integrity_segments : 0
/sys/block/sdc/queue/zoned : none
/sys/block/sdc/queue/scheduler : [mq-deadline] kyber bfq none
/sys/block/sdc/queue/io_poll : 0
/sys/block/sdc/queue/discard_zeroes_data : 0
/sys/block/sdc/queue/minimum_io_size : 4096
/sys/block/sdc/queue/nr_zones : 0
/sys/block/sdc/queue/write_same_max_bytes : 33550336
/sys/block/sdc/queue/max_segments : 128
/sys/block/sdc/queue/dax : 0
/sys/block/sdc/queue/physical_block_size : 4096
/sys/block/sdc/queue/logical_block_size : 512
/sys/block/sdc/queue/virt_boundary_mask : 0
/sys/block/sdc/queue/zone_append_max_bytes : 0
/sys/block/sdc/queue/io_timeout : 30000
/sys/block/sdc/queue/nr_requests : 256
/sys/block/sdc/queue/write_cache : write back
/sys/block/sdc/queue/stable_writes : 0
/sys/block/sdc/queue/max_segment_size : 4294967295
/sys/block/sdc/queue/rotational : 1
/sys/block/sdc/queue/discard_max_bytes : 0
/sys/block/sdc/queue/add_random : 1
/sys/block/sdc/queue/discard_max_hw_bytes : 0
/sys/block/sdc/queue/optimal_io_size : 0
/sys/block/sdc/queue/chunk_sectors : 0
/sys/block/sdc/queue/iosched/front_merges : 1
/sys/block/sdc/queue/iosched/read_expire : 500
/sys/block/sdc/queue/iosched/fifo_batch : 16
/sys/block/sdc/queue/iosched/write_expire : 5000
/sys/block/sdc/queue/iosched/writes_starved : 2
/sys/block/sdc/queue/read_ahead_kb : 4096
/sys/block/sdc/queue/max_discard_segments : 1
/sys/block/sdc/queue/write_zeroes_max_bytes : 33550336
/sys/block/sdc/queue/nomerges : 0
/sys/block/sdc/queue/zone_write_granularity : 0
/sys/block/sdc/queue/wbt_lat_usec : 75000
/sys/block/sdc/queue/fua : 1
/sys/block/sdc/queue/discard_granularity : 0
/sys/block/sdc/queue/rq_affinity : 1
/sys/block/sdc/queue/max_sectors_kb : 1280
/sys/block/sdc/queue/hw_sector_size : 512
/sys/block/sdc/queue/max_hw_sectors_kb : 16383
/sys/block/sdc/queue/iostats : 1
Array is running on systems with 48 cores, 96GB RAM with no other load.
stripe_cache_size = 32768
md0_raid6 process is using 50-75% cpu.
14TB hdds in 36 drives array are: WDC WUH721414AL5201
Each drive in has >200MB/s sequential read/write when tested by fio.
sync_speed_min/sync_speed_max is set to 200000.
36 drives are connected as JBOD via two controllers LSI SAS3008
PCI-Express Fusion-MPT SAS-3
Both controllers are in PCI-E 3.0 x8 slots: LnkSta: Speed 8GT/s (ok),
Width x8 (ok)
Iostat for this array shows:
9738.60 r/s
38956.00 rKB/s
0 rrqm/s
4.00 rareq-sz
Why there are so many 4KB IOPS issued to drives ? With other raid6
arrays during resync i always have rareq-sz at least 200KB and IOPS at
least 10x lower.
I was trying setting group_thread_cnt = 4. This was helpful on other
arrays but on this array it only resulted in increase in CPU iowait
and resync speed decrease to 33MB/s.
Regards,
Marcin Wanat
