Fwd: Re: Strange ZFS performance

[Bob Friesenhahn]

On Mon, 5 Apr 2010, Mikle Krutov wrote:
> Any information i could provide to help us know what's the source of the problem?

The svc_t value I saw posted in one of your mails was outrageously 
large.  I suggest running

   iostat -x 30

while doing long-duration write and see what the actual values are. 
It seems likely that you are overrunning what your controller or disk 
is capable of handling and this is creating an I/O backlog which is 
far greater than what it would be if zfs had queued fewer 
simultaneous requests.

It may be that tuning zfs_vdev_max_pending to a small value may help 
keep your controller from being overloaded.

Bob
--
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/