From: Francisco Reyes (listsstringsutils.com)
Date: Mon Oct 02 2006 - 10:04:16 CDT

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Sandy Drobic writes:

>> Imap processes.
>
> In that case no fiddling with Postfix settings will alleviate the problem.

So far eliminating two of the 3 SQL lookups helped.
Also moved IMAP connections to a gigabit switch... so hopefully IMAP
connections will get served faster.
  
> Increasing the cache size will help a bit

Don't think these controllers can take any more memory.

>, also adding one or two more
> hdds to the raid to spread the I/O over more hdds. How many hdds are there
> in your raid? Which raid level?

8 disk totals. 6 in RAID 10 and 2 as hot spares. I wanted to get all 8 in
the RAID, but the owner preferred to have them as hot spares.
 
> Though I am afraid your system is just overtaxed. In that case you can
> probably only decrease the load or increase the system performance with
> better hardware.

Thanks for the help. After a couple of weeks of looking into this I was
starting to get that impression. Waiting to see how the last changes help
the system. Also plan to remove the last SQL lookup today.
  
> You need some hard figures to find out if it is sufficient to tweak your
> system or you need new hardware.

Started to work on that too. Basically all the heavy SMTP domains were moved
to these machines and I think we need to move those domains to a new machine
with a SCSI setup.

We are also considering to move to Dovecot. As customers let email pile up
on directories Courier takes longer and longer to open large folders.

Our early testing with Dovecot looks very promissing. The first time a
directory is read it takes long, but still quicker than Courier, and after
that access is through index files which seems noticeable faster than
Courier. Hopefully a change in IMAP will decrease I/O tso here will me more
resources for Postfix.

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