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Re: Performance ext3/hardware raid



On Apr 05, 2002  01:29 +0200, Michael Renner wrote:
> The test-partitions are on a ICP Vortex GDT8523RZ which runs in a RAID10
> setup, the filesystems got created/mounted with standard settings (except
> 1024 byte blocksize on ext2/3 partitions). The noatime mount option hardly
> affected the performance, switching from ordered to writeback in ext3 also
> didn't change the results notable. I didn't dare to play around with
> reiserfs mount options because i hardly have any knowledge about their
> drawbacks.

I would suggest benchmarking two things (independently and together):
1) running ext2/ext3 with a 4kB block size.
2) running ext3 with data=journaled

While the bonnie++ benchmark may not show good results with #2, you will
find that ext3 with data=journaled + sync I/O from MTAs has a very good
performance.  You will probably need to make the journal larger in this
case (4x as large as the amount of email you will handle in 5 seconds),
or 128MB-256MB or so.

I would suggest using something like "postal" to benchmark a mail server.

> As you can see the random delete results on the ext2 drive are way better
> than reiser and ext3, and this is something a mailserver does on a regular
> basis when serving pop-boxes (especially if a user has say 2000 new mails
> in his mailbox and all he does is a "stat" and then disconnects the popd
> has to move all the mails from the "new" to the "cur" dir).

It's a journaling issue (ext3 actually writes to disk for deletes, while
ext2 may skip writing a lot of stuff that has been invalidated before it
needs to be written).

Cheers, Andreas
--
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert





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