Jeremy,

Sysstat is just showing you the most utilized disk.  You need statit to show you the disk utilization of all disks.  Here’s how:

Toaster>priv set advanced

Toaster*>statit –b

Toaster*>sysstat –x 1

Wait 30 seconds or so and verify that disk util > 80% most of the time

Toaster*>statit –e

You will get a flood of text (you may need to increase your buffers), scroll up until you see something like this:

disk             ut%  xfers  ureads--chain-usecs writes--chain-usecs cpreads-chain-usecs greads--chain-usecs gwrites-chain-usecs

/sata_aggr0/plex0/rg0:

0f.16              2   1.13    0.18   1.00 21130   0.59  13.49  1467   0.35   8.13   414   0.00   ....     .   0.00   ....     .

0f.17              2   1.26    0.18   1.00 47250   0.72  11.41  1364   0.35   8.13   369   0.00   ....     .   0.00   ....     .

0f.18              4   6.00    5.25   1.37  9595   0.46  14.98  1270   0.29   8.37   491   0.00   ....     .   0.00   ....     .

0f.19              4   5.27    4.72   1.23 10874   0.32  21.44  1308   0.24   9.19   432   0.00   ....     .   0.00   ....     .

0f.20              4   5.03    4.45   1.15 10307   0.36  18.74  1407   0.22   9.89   440   0.00   ....     .   0.00   ....     .

0f.21              4   5.22    4.65   1.12 10573   0.37  18.40  1462   0.20  10.73   556   0.00   ....     .   0.00   ....     .

0f.22              4   5.12    4.55   1.08 11421   0.37  18.33  1505   0.21  10.19   487   0.00   ....     .   0.00   ....     .

0f.23              4   5.09    4.45   1.13 10442   0.39  17.68  1575   0.25   9.30   466   0.00   ....     .   0.00   ....     .

0f.24              4   5.19    4.62   1.19 10679   0.34  20.07  1497   0.23   9.53   531   0.00   ....     .   0.00   ....     .

0f.25              4   5.14    4.48   1.25 10350   0.38  18.00  1624   0.29   8.22   470   0.00   ....     .   0.00   ....     .

0f.26              4   5.17    4.53   1.19 11904   0.35  19.20  1574   0.29   8.73   610   0.00   ....     .   0.00   ....     .

0f.27              4   5.43    4.78   1.05 13052   0.33  20.47  1431   0.32   7.40   720   0.00   ....     .   0.00   ....     .

The first field is the disk and the second field is the disk utilization over the period you ran the statit.  If you want more accurate results you can run the statit for longer.

Finally:

Toaster*>priv set ;)

Toaster>

Most typically a few hot disks in an aggregate are the outcome of adding only a couple of disks and creating a very small raid group.  You should do two things in that scenario:

Add more disks until the raid group is fully populated (and make sure raid size = 14 or 16)

Run reallocate on the volumes in the aggregate to spread out the IO against all disks equally

HTH,

Hadrian

From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Page, Jeremy
Sent: Wednesday, June 04, 2008 11:32 AM
To: toasters@mathworks.com
Subject: How to identify a hot disk

So I am getting the following when running  sysstat –u. As far as I know nothing should be hitting the array hard enough to drive disk utilization to 100%, much less hold it there. What can I do to further determine what’s causing this?

All of my storage is NFS based at this time.

29%     799 44261  1344  14900  54402     0     0    38   93%  46%  F  77%

 29%     896 43727  1938  14643  54488     0     0    38   93%  43%  F  94%

 28%     734 43831  1102  13251  54881     0     0    38   93%  44%  F  77%

 CPU   Total    Net kB/s    Disk kB/s    Tape kB/s Cache Cache  CP  CP Disk

       ops/s    in   out   read  write  read write   age   hit time ty util

 31%     876 53275  1354  12054  61719     0     0    39   93%  53%  F  80%

 13%     264  8377   369  15069  14423     0     0    39   92%  31%  2  94%

  8%     107   674    33  13300   5331     0     0    39   92%  30%  T  94%

  7%     101   601   112  13263   1026     0     0    39   92%   7%  T 100%

  8%     100   626    55  15145    989     0     0    40   92%   6%  T  85%

  8%      76   520    76  13809   2049     0     0    40   92%  13%  T 100%

  8%      96   602    63  13637    893     0     0    40   92%   5%  T  93%

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