Maybe that's why I think of the iowait as being "high".... I never
ever saw any number other than 0.0% on a RH9 machine. This application has
been migrated from RH9 to RHEL. The iowait numbers work in RHEL. This is
not just in top, but vmstat as well.
But, I rarely saw 10% sys on the old RH9 system. So, if iowait was
lumped in with sys, then iowait had to be less than 10% on the RH9 system.
At 03:00 PM 8/10/2005 -0700, you wrote:
Mike,
I can't think of a way to tell what process is causing iowait. I remember
vagely some option to 'top' telling you how many system calls that a process
has made, but I don't see that now, anyone else?
It's possible we're barking up the wrong tree, however. Top won't report
iowait at all in RH9. It'll just lump iowait and other system calls in the
'sys' figure. If you peak at 10% iowait when you have 85% user, then you
know the disk speed won't kill you, the CPU will be the next thing to upgrade.
On the other hand, disk is pretty much the thing that's slowed me down more
than everything else for 90% of server apps, and it's also the biggest pain
to upgrade when you decide it's insufficient.
Dave
On Tue, Aug 09, 2005 at 08:45:03PM -0700, Michael J McCafferty
([EMAIL PROTECTED]) wrote:
Subject: What process is causing iowait ?
Message ID: <[EMAIL PROTECTED]>
> All,
> How do I determine which process is responsible for some iowait on
a RHEL 3
> server ?
> I moved a bunch of stuff over from RH9 to a new RHEL server, with
similar
> hardware (same RAID Card, larger drives, faster cpu, faster RAM, same Mobo,
> same network). I also upgraded an application.
> I might be just a little extra sensitive now that I am looking for
bugs, but
> I notice that there are short periods (~10 seconds ?) of 10% iowait. I
don't
> recall ever seeing any iowait on the RH9 system before the applcation
upgrade.
> Otherwise, the load in terms of users, bandwidth and type of work is
the same.
> I plan to add muchmore load in the future, so I want to locate any
bottlenecks
> early.
>
> Thanks,
> Mike
>
>
> --
> ************************************************************
> Michael J. McCafferty
> Principal, Security Engineer
> M5 Hosting
> 858-576-7325 Voice
> http://www.m5hosting.com
> ************************************************************
>
>
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