iostat = 100% busy - whats causing this

From: Gary Brett (gary.brett@fidessa.com)
Date: Wed Apr 18 2007 - 05:44:14 EDT


Hi there

I have a Solaris 10 x4100 (running sybase) with something making masses
of read requests on one of my disks

# iostat -xPnse
                          extended device statistics ---- errors

---
  r/s        w/s   kr/s      kw/s wait actv wsvc_t asvc_t  %w  %b  s/w
h/w  trn   tot    device
205.6    1.6 2696.8    8.0  0.0  7.2    0.0   34.9   0       100   0
0     0     0   c0t3d0s5
[other lines omitted]
#
As you can see I have a %b (percent busy) of 100% and 2696.8 kb/s read
activity. The Sybase processes on this box are experiencing problems and
I just wondered if anybody knew an easy way of finding out which process
is hammering this disk with reads ??? Looking at prstat, there is no
obvious way of telling what is reading from the disk. I suspect it is a
looping or faulty query or something like that, but if there's any way
of digging deeper into this then it would be great to know
Any help on this would be greatly appreciated
Cheers
Gary
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