Re: Interesting disk throughput performance problem

Jakob Østergaard
2001-07-22T10:30:41Z

On Sat, Jul 21, 2001 at 11:33:13PM -0400, Jimmie Mayfield wrote:
> Hi. I'm running into some disk throughput issues that I can't explain.
> Hopefully someone reading this can offer an explanation.
>
> One of my machines is running 2.4.5 and has 2 hard drives: a 7200 rpm
> ATA100 Maxtor and a 5400 rpm ATA33 IBM. Each drive is a master on its own
> controller (AMI CMD649 as found on the IWill KT266-R). Both drives contain
> reiserfs 3.6x filesystems.
>
> By all local benchmarks, the 7200 rpm drive is the faster drive. But this
> doesn't seem to be the case for large files originating from remote clients.
> Witness:
....
> So I tried the test locally: with the file stored on the 5400rpm drive,
> scp it to localhost and write it to the 7200rpm drive. Results were a little
> below 10MB/sec (CPU near 100% presumably due to encrypting/decrypting on
> the fly).
>
> Any ideas why the 7200rpm drive performs so poorly for remote clients but
> performs wonderfully well when those same operations are performed locally?

This is a wild guess:

Try cat /proc/interrupts

Would the 7200 rpm drive controller happen to share an IRQ with your NIC ?

If so, something is horribly wrong since that shouldn't give that kind of
performance penalty. But it's my best guess :)

--
................................................................
: jakob@unthought.net : And I see the elder races, :
:.........................: putrid forms of man :
: Jakob Østergaard : See him rise and claim the earth, :
: OZ9ABN : his downfall is at hand. :
:.........................:............{Konkhra}...............: