improving concurrency/performance

John Madden jmadden at
Fri Nov 4 14:01:00 EST 2005

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. :)


John Madden
UNIX Systems Engineer
Ivy Tech Community College of Indiana
jmadden at

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