Re: [Dovecot] Dovecot NFS Indexes and IMAP Migration

[Timo Sirainen]

On Feb 27, 2008, at 8:49 AM, Andy Dills wrote:

From reading the docs, it appears I would not be able to use the dovecot

LDA due to locking issues (bummer), and I should configure dovecot to

than on the netapp.

store index files on a local disk of the primary pop/imap server rather

I don't think locking is an issue. NFS caching is more problematic. But with v1.1's mail_nfs_*=yes settings there should be no problems with storing indexes on NFS.

My first question would be, how much of a performance hit should I expect from having to update the indexes when mail is checked rather then when mail is delivered since I can't use the LDA? Is this a minor issue like I

expect, or can it be something the user actually notices when checking
mail?

It's a minor issue usually.

In a worst case scenario, if the pop/imap server is down, and another

with a few hundered megs, several thousand messages? I'm wondering if,
since I have plenty of overhead available on the netapp, I should just
store the indexes there in case another server must be used.

server is used, how long would it take to create an index for an account

The actual index file creation is really fast. More problematic is losing dovecot.index.cache file for clients that want to fetch/search old data. But Courier/Binc did no caching at all, so Dovecot wouldn't be any worse.

First off, I can't seem to find any info on a way to create an initial

use for this? I'm sure I just overlooked it.

index file for all of the mailboxes. Can anybody suggest a command I can

I don't think you should worry about it. Like I said, the dovecot.index.cache file generation is the slow part. But since its generation depends entire on what fields client is using, you can't really pregenerate it properly anyway. http://wiki.dovecot.org/IndexFiles tries to describe this. http://imapwiki.org/Benchmarking might have more understandable explanation as well.

Fortunately, courier is used for normal imap on 143, bincimap is only used

for webmail. So, it would seem that metadata from bincimap could be
ignored; the only thing it would seem important to preserve is mailbox
subscriptions. Please correct this assumption if I'm wrong.

Right.

So, it seems like my best option is to modify the

been a while since I've done anything substantial in perl.

courier-dovecot-migrate.pl script to consider the mailboxes subscribed to via bincimap. Here's a modified convert_subscriptions that seems to work well in limited testing, feel free to point out any idiot mistakes, it's

I'm not that great perl coder either. :)

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