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Re: slowwww IMAP

On Thu, 5 Dec 2002, Justin Ryan wrote:

> Hiya Debian-users,
> On my mail server running Debian Woody with UW-IMAP and Sendmail, I've
> got ~200M of mail archived into several mbox folders in ~/Mail that I
> check both with IMAP and with mutt.  As the folders have gotten larger,
> access has slowed significantly.  I beleive part of this was due to the
> data becoming fragmented on disk, and so I stopped all mail services,
> created a tar of ~/Mail, moved ~/Mail to ~/Mail.old, and untarred the
> files back into ~/Mail.  This caused a significant increase.........for
> a short while.

It's possible but not the real problem.  the real problem is inherent in
the mbox format, all the messages are kept in one file and the entire file
has to be read into memory.  Maildir helps because each message is a
seperate file.  (But the downside is it could waste more space on disk
though this can be worked around with by using file systems like

> In any case, I'm trying to find a way to make my IMAP access faster.
> I've considered converting to Maildir format but can't find an easy way
> to convert my existing mailboxes.

Debians' uw-imapd package already has the maildir patches the other
respondent was talking about applied.  So an easy way to do this would be

1.  Create a new mailbox as a maildir.
2. Using your mail client, move all the messages from the old folder to
   the new one.

The IMAP server will take care of the format conversion for you.

> What I'm asking is, essentially, if there is any good documentation on
> moving from a very basic setup (unix mbox, sendmail going to unix
> accounts, etc..) to what seems to be a more complex setup.  As I
> understand it, courier likes to use its' own account database, and it
> would not be simple for procmail to filter into Maildirs.

although I've forgotten the exact voodoo right now, it is in fact easy to
make procmail deliver to maildirs.

> If there are ways that I can improve performance _without_ mucking my
> config around, it would be preferred,

How about deleting some of your mail? :)

Jaldhar H. Vyas <jaldhar@debian.org>
It's a girl! See the pictures - http://www.braincells.com/shailaja/

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