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klement

Member

Registered: 2015-01-27

Posts: 5

raid5 always utilized to 100%

Hi, I noticed that this happens on my system:

# iostat -mxd 1
Device:         rrqm/s   wrqm/s     r/s     w/s    rMB/s    wMB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
sdb               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
sdc               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
sdd               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
dm-0              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
dm-1              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00  2779.78    0.00    0.00    0.00   0.00 100.10
dm-2              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
dm-3              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
dm-4              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
dm-5              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

over time, it gets worse, avgqu-sz goes into millions even though the system is basically idle.

md0 is a raid5 device comprised of 3 physical hdds.

# cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid5 sdd[3] sdc[1] sdb[0]
      5860270080 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
      bitmap: 0/22 pages [0KB], 65536KB chunk

unused devices: <none>

On top of the raid5, there is LUKS encrypted volume.
I don't see any real performance issue, just wondering why the average queue size is high.
I did a reboot and before unlocking the array, the avgqu-sz was steadily 19 and it showed 100% utilization.
Can somebody please explain?

Thanks,
Klement

Last edited by klement (2015-05-09 05:38:12)

jasonwryan

Anarchist

From: .nz

Registered: 2009-05-09

Posts: 30,424

Website

Re: raid5 always utilized to 100%

Please use code tags when pasting to the boards https://wiki.archlinux.org/index.php/Fo … s_and_code

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