Irregular disk IO and poor performance (possibly after reading a lot of data from pool)

[Dmitriy Makarov]

InterNetX - Juergen Gotteswinter-2 wrote
> one/more disks broken or tend to die soon?

Nope, at least does not seem like that. Smarts are OK for all drives:

OK - HDD S.M.A.R.T health: src=0, rsc=0, rec=0, cps=0, ou=0,
HEALTH_STATUS=PASSED 

Drives are not so old either ~1year.

I doubt it has anything to do with the drives for two reasons:
 * paired devices in the mirror behave pretty much exactly
 * different pairs have 0 wtire I/O at different points of time and it's not
like seconds, it is a matter of minutes.

It seems as if ZFS decides to ignore some mirror devices for unknown reason.
Randomly.
Sometimes just 2-3 of 18 are idle. Sometimes it's 17 of 18! Nedless to say
in that moment, 
that one poor mirror is doing all the hard work by itself. At which point
system almost freezes, 
all I/O bound processes are blocked waiting for disk.



--
View this message in context: http://freebsd.1045724.n5.nabble.com/Irregular-disk-IO-and-poor-performance-possibly-after-reading-a-lot-of-data-from-pool-tp5969896p5969924.html
Sent from the freebsd-fs mailing list archive at Nabble.com.