On 05/25/2016 09:54 AM, Kelly Lesperance wrote:
What we're seeing is that when the weekly raid-check script executes,
performance nose dives, and I/O wait skyrockets. The raid check starts out
fairly fast (20000K/sec - the limit that's been set), but then quickly drops
down to about 4000K/Sec. dev.raid.speed sysctls are at the defaults:
It looks like some pretty heavy writes are going on at the time. I'm not
sure what you mean by "nose dives", but I'd expect *some* performance
impact of running a read-intensive process like a RAID check at the same
time you're running a write-intensive process.
Do the same write-heavy processes run on the other clusters, where you
aren't seeing performance issues?
avg-cpu: %user %nice %system %iowait %steal %idle
9.24 0.00 1.32 20.02 0.00 69.42
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 50.00 512.00 20408.00 512 20408
sdb 50.00 512.00 20408.00 512 20408
sdc 48.00 512.00 19984.00 512 19984
sdd 48.00 512.00 19984.00 512 19984
sdf 50.00 704.00 19968.00 704 19968
sdg 47.00 512.00 19968.00 512 19968
sdh 47.00 512.00 19968.00 512 19968
sde 50.00 704.00 19968.00 704 19968
sdj 48.00 512.00 19972.00 512 19972
sdi 48.00 512.00 19972.00 512 19972
sdk 48.00 512.00 19980.00 512 19980
sdl 48.00 512.00 19980.00 512 19980
md127 241.00 0.00 120280.00 0 120280
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