Performance of disk i/o with 3ware

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

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@xxxxxxxxxxxxxxxxxxxxxxxx:/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@xxxxxxxx

Anyone an idea,
a) why systat -vmstat shows so small busy values?
b) how to debug it further?

Sincerly

Nico

--
Think about Free and Open Source Software (FOSS).
http://nico.schottelius.org/documentations/foss/the-term-foss/

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