Lelsie Rhorer wrote:
This sounds like a filesys problem rather than a RAID problem.
I considered that. It may well be.
One thing that can cause this sort of behaviour is if the filesystem is in
the middle of a sync and has to complete it before the create can
complete, and the sync is writing out many megabytes of data.
For between 40 seconds and 2 minutes? The drive subsystem can easily gulp
down 200 megabytes to 6000 megabytes in that period of time. What synch
would be that large? Secondly, the problem occurs also when there is
relatively little or no data being written to the array. Finally, unless I
am misunderstanding at what layers iostat and atop are reporting the
traffic, the fact all drive writes invariably fall to dead zero during an
event and reads on precisely half the drives (and always the same drives)
drop to dead zero suggests to me this is not the case.
If you have things setup such that you have lights on the disks, and
can check the lights when the event is happening, often if a single
drive is being slow it will be the only one with its lights on when
things are going bad.
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