Performance of disk i/o with 3ware

[Manjunath R Gowda]

On 11/6/07, Nico -telmich- Schottelius <
nico-freebsd-performance at schottelius.org> wrote:
>
> Hello!
>
> I've the problem that sometimes there are many disk waiting processes
> (sysctl -n vm.vmtotal), but systat -vmstat shows da0 and da1 busy with
> 0-10%.



I woudn't worry about how many are sleeping. But, How long they sleep would
be interesting data.

I guess that the disk i/o is at about 100%, but wondering why I see
> those strange values.



Why do you think it should be 100%? Are you running any disk I/O intense
application?

System Information:
>
> - Disks are attached to 07:01.0 RAID bus controller: 3ware Inc 9550SX
> SATA-RAID
>
> u0216# uname -a
> FreeBSD u0216.nshq.netstream.com 6.2-RELEASE FreeBSD 6.2-RELEASE #0: Wed
> Oct 31 14:53:00 CET 2007 root at u0216.nshq.netstream.com
> :/usr/obj/usr/src/sys/SMPPAEQUOTA  i386
>
> => kernel contains 3ware patches from CVS, marked for inclusion in 6.3,
>   because we've seen many times a freeze on that system before
>
> - Disks are 10k rpm sata disks.
> - Board is a Supermicro X7DB8, processor is a quad core Xeon,
> E5345 at 2.33GHz.
>
> Anyone an idea,
>   a) why systat -vmstat shows so small busy values?
>   b) how to debug it further?


You can try experimenting  with diffrent I/O loads to make sure that there
is a problem before start debugging it.


-Manjunath