[Dovecot] Large & busy site, NFS with deliver only servers

[Dean Manners]

Timo / Others,
 
I have been working on a new installation for a fairly busy site, and after
many weeks of tribulation have come to an architecture Im happy with:
2x Debian (2.6.18) - MXing machines running Postfix / MailScanner /
Dovecot-LDA (A slightly patched RC17 for prettier Quota bounces)
2x Debian (2.6.18) - Mail retrieval machines running Dovecot IMAP/POP3
(Currently RC17)
3x Node Isilon NFS cluster (NetApp type devices)
 
I chose Dovecot-LDA over Postfix-Virtual / Maildrop / Procmail due to its
hassle free auto creation of new user maildirs, and the funkyness of built
in Sieve functionality.  The on the fly indexing sounded like a bonus at the
time.  However as Im sure all people who stress test with index's stored
over NFS find, index locking makes for some 'spectacular crashes' (see
others previous posts).  
I have tried out the recommended mount options and locking methods to no
avail.  Once under some stress, say ~60 messages a minute from the two front
end machines, understandably the index's get pickled instantly.  So as a
hack way around the index locking problems, I have configured the MXing
machines to index locally to no where (/tmp) - and deal with the very
slightly slower IMAP/POP3 performance on the retrieval side.  
 
Is there way to tell/patch Dovecot-LDA not to bother with indexing? So Im
not creating unused index files.
 

Cheers
__________________________________________
Dean Manners