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Re: High load on Squid server after change from reiserfs to ext3



----- Original Message -----
From: "Andreas Dilger" <adilger clusterfs com>
To: "Andreas Jung" <andreas zope com>
Cc: <ext3-users redhat com>
Sent: Friday, May 24, 2002 13:35
Subject: Re: High load on Squid server after change from reiserfs to ext3


> On May 24, 2002  13:01 -0400, Andreas Jung wrote:
> > We are running Zope behind Squid 2.4Stable6 with squid in acceleration
mode.
> > The squid box (dual Pentium III 1 GHz, RH 7.2, Linux 2.4.9-21smp, 2GB
Ram)
> > has during busy hours a normal load of 0.2-0.3 . From time to time
> > we see spikes over some hours where the load average of the machine
> > is higher than 1.5 although there are no spikes in the CPU
> > utilization. Also there is no increase in the number of incoming
requests.
> >
> > The only change we made was the switch from reiserfs to ext3 for the
cache
> > partition since reiserfs corrupted its partition some time ago.
>
> One simple question - does the increase in the load value actually
> affect squid performance?  You say there is no increase in CPU
> utilization.  That may be good or it may be bad, depending if the "idle"
> CPU is actually waiting on I/O to complete.
>
> What does the output of vmstat on both systems show?  Please send two
> traces, one during low load and one during high load.

Our big brother diagrams show that the CPU utilization remains *low* all
the time. I have been running vmstat on both machines when one of the
machine
had a spike. But both machines showed more ore less identical vmstat output:
CPU was about 85% idle, no swapping, not much interrupts and context
switches.
In general, vmstat showed a perfect behaviour except that the load average
went up on one box.


Andreas





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