 | | | Taroon U3 sluggish issues | Taroon U3 sluggish issues 2004-11-05 - By Marc Wiatrowski
Back
Originally we had a Dell PE650 running RH 7.3 (kernel 2.4.18-10) with a
2.4 GHz P4 and 512M memory. The application running on this server has many
processes, not much local disk io, lots of NFS disk activity to a couple
NetApps,
and lots of DB interaction with multiple different machine running Postgres.
The load on this box was averaging about 6.
Recently we upgraded the machine to another Dell PE750 RHEL 3.0 update 3
(kernel vmlinuz-2.4.21-20.Elsmp) 2.8 GHz P4, 2G memory, and with hyper
threading
turned on. So this machine was running the same server jobs as before but
now
the load jumped up more than double to about 15. I realize load is pretty
general
especially between two different machines, but the machine was noticeably
much
slower and applications where taking much longer to run now.
We have tried turning off hyper threading in the bios and went to the
non-smp kernel
and that had no effect. Tried playing with inactive_clean_percent and this
had
no noticeable effect either.
One kicker was we then tried the U2 kernel 2.4.21-15 leaving everything else
at U3 and the machine got noticeably better The load dropped down to about
10.
The iowait still stayed close to 100%. So it was running better, but still
not as
good as the "slower " machine running RH 7.3
Then we found NFS defaults had changed from async to sync. Forcing async
appears
to have dropped the load down to a livable average of about 6.
Network traffic appears to have stayed the same through all of this and
swapping
has never been an issue. Memory usage is less than 500M. Iowait had
generally
been about 100% up to the async change. After that its dropped down quite a
bit.
In all cases Postgres is the same version and as far as NFS its always been
udp,
version 3.
Was wondering if anyone is noticing similar issues or know of anything else
that
has changed between the 2.4.21-15.0.3 and 2.4.21-20 kernels? Anything else I
could
look at?
thanks for any help,
marc
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