On 14.2.2010, at 3.31, Stan Hoeppner wrote:
I can't see how the metadata sharing of say GFS2 is going to create
any serious performance impact on a cluster of dovecot servers using GFS2 and a
shared SAN array especially if using maildir.
While I use GFS shared on a cluster with dovecot for mbox and think the performance rocks, this really depends on the setup (mbox may be worse than maildir, how much hardware you have for it, how you load balance, etc) and what you consider good/bad performance (what is fast to me might be slow to you) as well as of course scale (might work for 2K users, but what about for 200K or 1.5M).
If the load balancing is implemented correctly and a given user is only hitting one dovecot server at
any one point in time, there should be few, if any, shared file locks. Thus, no negative impact due to shared locking.
This ignores the delivery of mail to the user (again, not so bad for maildir but a killer for mbox). If the delivery is on a separate box than dovecot your can have lock contention...
Also there may be other things to cause lock contention like backups, admin cron jobs to check things, etc.
Anyway, I run dovecot in a cluster without any issue, but that is because of my client base and performance expectations (and some real nice hardware).
-- Eric Rostetter The Department of Physics The University of Texas at Austin
Go Longhorns!