[Dovecot] Current state of mulit-server NFS setups

[Justin McAleer]

Hi list,

I've been perusing the list archives, but I couldn't find a recent, 
definitive answer to what I'd like to know. I'm looking to set up a new 
batch of servers to migrate ~160,000 accounts, spread across several 
domains, onto (from CommuniGate). Last year I worked with the earlier 
beta/RC versions of Dovecot, so I'm generally familiar with the setup 
required. However, a lot of development has been done since I was last 
dealing with it.

So, what I'd like to end up with is a load balanced group of servers 
providing pop and imap access with quota support using an NFS 
filesystem. We have a new Netapp device (forget the actual model) that 
can do SAN/iSCSI/NFS. We tried using various clustered filesystems 
previously, but the performance/stability issues were a nightmare, so 
I've fallen back to NFS (or perhaps SAN if users can't hit any server in 
the group).

So, what does my dovecot setup need to be? I've seen some people say 
they disable indexing in the LDA, but allow pop/imap to index. Some say 
the attribute cache needs to be disabled, which I'd think would be worse 
than just disabling indexes. Some say indexes should be kept on local 
disk (dedicated server for users), and others seem to report problems 
even when doing so. Is there a general consensus?

I was also wondering if dovecot's sanity checking on the indexes would 
allow each server in a balanced group to keep indexes on local disk (so 
if the maildir has changed on another server, dovecot rebuilds it). If 
so, does that take away all performance gains from having indexes at all?

Thanks for any info you all can provide.