[Orca-users] Re: Determining Disk I/O Bottlenecks with Orca

Blair Zajac blair at akamai.com
Fri Mar 24 10:30:55 PST 2000

I think we'll have to trust Adrian on this one, as I'm not up
on all the details regarding busy disks.

Probably the best thing is to extend orcallator.se and
orcallator.cfg to measure and plot the data described in
Adrian's articles.

I'll gladly accept and include any patches to these programs
(hint, hint).


Charles Dennett wrote:
> From: Charles Dennett <charles.dennett at kodak.com>
> I've installed Orca on a whole bunch of systems here.  Some of
> us met yesterday to discuss Orca and compare it to something
> else we had been using.  This other stuff was home grown and
> uses simple UNIX commands (df, vmstat, iostat, ps swap, netstat)
> to collect data and produce some rudimentary graphs.   Orca
> is far superior.
> However, there was one item we collected that Orca seems not to
> have.  That is the disk service time as collected by iostat -x.
> As a side note, I read the docs for the SE script siostat.se and
> saw the reference that what iostat -x puts out is really not the
> disk service time and read Adrian's (God bless him) article
> that was mentioned there.  I have not fully studied it yet but
> I get the gist of what he is saying.  We used this (erroneous)
> data to help figure out where disk I/O bottlenecks were.
> If the service times went too high we started looking at distributing
> the loads across new or other disks.  We based our rules on the
> ones Adrian specified on page 228 of the first edition of
> his book.  I also have the second edition of Adrian's book and
> can see the same article in Chapter 8.  I'm studying that
> chapter now.
> The way orca is now, the only measurement of disk activity I see
> is the Disk Run Percent graph (which I believe is showing the
> % busy of the disk, right?)  So, using orca, how would one
> determine if an I/O bottleneck existed?  Would it be useful to
> extend orcallator.se and orca to collect and display data similar
> to what the siostat.se script collects? Is it a simple case of
> keeping the Disk Run Percent below a certain value?  Something
> else?
> Thankls for any words of wisdom anyone can provide.
> --
> Charlie Dennett
> Eastman Kodak Company, Rochester, NY
> Sitemaster http://www.kodak.com
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