Alexey Popov wrote:
Kris Kennaway wrote:
what is your RAID controller configuration (read ahead/cache/write
policy)? I have seen weird/bogus numbers (~100% busy) reported by
systat -v when read ahead was enabled on LSI/amr controllers.
I tried to run with disabled Read-ahead, but it didn't help.
I just ran into this myself, and apparently it can be caused by
"Patrol Reads" where the adapter periodically scans the disks to look
for media errors. You can turn this off using -stopPR with the
megarc gg port.
Oops, -disPR is the correct command to disable, -stopPR just halts a
PR event in progress.
Wow! Really disabling Patrol Reads solves the problem. Thank you!
I have many amrd's and all of them appear to have Patrol Reads enabled
by default. But the problem happenes only on three of them. Is this a
hardware problem?
I am not sure, maybe for some reason the patrol reads are not
interfering with other disk I/O so much (e.g. the hardware prioritises
them differently or something).
Anyway, glad to hear it was resolved.
Kris
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