dovecot local indexes and multiple servers

[alex]

Hi,

I've been testing mdbox with local indexes on our nfs based directors + 
multiple imap/lda/pop3 server setup. The performance is noticeably 
better than maildir with indexes on nfs, so I'd like to make this work.

About the possible direction to other servers the wiki says that it will 
create a new index 'on the fly'. That is true, but after the index is 
recreated, Thunderbird (imap) re-downloads all the messages and sees all 
those messages as unread again!

This is probably quite logical as the message status is only kept in the 
indexes, but this is not very customer friendly. Is there a way to avoid 
this problem?

I'd rather not manually sync those local indexes between our servers. In 
fact, I was planning on deleting (old) indexes when a user moved to 
another server or even if they haven't checked their mail for XX days.
with up to 10Gb mailboxes the indexes themselves can get up to 20-40Mb 
for a mailbox. that amounts to quite a lot of storage for 200k+ users.

Thanks,
Alex.