[Dovecot] benchmark dovecot

[Mark Zealey]

Thanks; these look interesting. We have a similar nas setup but we have
2 frontend dovecot servers connecting to it and store the indexes over
nfs. We also have around 10 mail servers running deliver to try to keep
the indexes on the nfs store up-to-date. Have you done any tests with
the speed of multiple boxes each maintaining a local index of the
mailbox? I suspect in this case keeping indexes on nfs would be the best
bet but I don't have anything to substantiate that claim...

Also one thing to note with storing things on nfs is that there are a
large number of broken kernels out there (they issue about 10* more nfs
lookup requests than they should) - centos 5.1 had these issues iirc
(though the centosplus kernel and centos 5.2 did fix it). Always give it
a good test before you change the kernel on your server... I assume you
are using nfs3; has anyone tried using heavily loaded nfs4 and seeing if
any better performance can be achieved?

Another thing - I found that dovecot's pop3 implimentation is worse than
courier's over nfs (wait state on our boxes is significantly increased).
I still don't really understand why this is; I suspect it's probably due
to to the indexes being created/updated though I thought these were
meant to be discontinued after a while if it is just a simple
login/fetch all operation. I only mention this because if you are
offering pop then you should really do the same benchmarks for that.

Mark