improving concurrency/performance

[Sergio Devojno Bruder]

John Madden wrote:
> I've had great experience with the performance of Cyrus thus far, but I'm testing
> a migration at the moment (via imapcopy) and I'm having some pretty stinky
> results.  There's no iowait (4 stripes on a 2Gbps SAN), no cpu usage, nothing
> waiting on the network, and still I'm seeing terrible performance.  I assume this
> points to something internal, such as concurrency on the db files.
> 
> I've converted everything to skiplist already, I've tweaked reiserfs's mount
> options, what little Berkeley still used appears to be ok (no waiting on locks and
> such), so I'm at a loss.  Is there a general checklist of things to have a look
> at?  Are their tools to look at the metrics of the skiplist db's (such as
> Berkeley's db_stat)?  Am I doomed to suffer sub-par performance as long as IMAP
> writes are happening?
> 
> Migration's coming on the 24th.  I'm now officially sweating. :)
> 
> Thanks,
>   John

In our experience FS-wise, ReiserFS is the worst performer between ext3, 
XFS e ReiserFS (with tailBLAH turned on or off) for a Cyrus Backend (>1M 
mailboxes in 3 partitions per backend, 0.5TB each partition).

--
Sergio Bruder