8.0-RELEASE: disk IO temporarily hangs up (ZFS or ATA related problem)

[Alexander Zagrebin]

> >> I doubt this is the problem, I have WD10EADS disks in my ZFS 
> >> array and I 
> >> see the same issue.
> >>
> >> It strikes me as extremely unlikely that both of us would have dud 
> >> disks..
> >>
> >> In any case it seems to be a general problem not limited to 
> >> one area of 
> >> the disk so a dud sector is an unlikely reason.
> > 
> > Big thanks for confirmation!
> > Your confirmation is important for me.
> > There should be a way to define where the bug is: in the 
> ata (or filesystem)
> > driver or in the drive's firmware....
> 
> Just another 'me too'.
> >From the moment I started using zfs and till this day I saw 
> this pattern when
> writing lots data to zfs - first high throughput and then 
> idle pause, and so on.

May be it usual write caching? See gstat or iostat output.
At my case gstat shows abnormal value of %busy (usually approx. 180%)
and very long ms/r and ms/w.

-- 
Alexander Zagrebin