[Dovecot] o/s tuning for imap
Kyle Wheeler
kyle-dovecot at memoryhole.net
Thu Sep 6 22:44:11 EEST 2007
On Tuesday, September 4 at 12:16 PM, quoth Ken A:
> I'm switching from a pop3 only dovecot install to a pop3/imap install and
> I'm wondering how many connections every 100 'normal' imap users might
> have/keep open?
Mmmm, I usually estimate that most of the time users keep one
connection open. Occasionally some clients (like Mail.app with the
IDLE plugin) keep two or three open at all times. Then of course,
there's occasional bursts where a client may open ten or more
connections, though because IMAP is asynchronous that's technically
unnecessary unless you're doing it to reduce latency (unlikely), but
some clients do it anyway.
So I'd leave a max of around 300-500 connections at minimum.
> I'm wondering if I need to tweak any o/s related things, like
> time_wait, etc. Any pointers would be greatly appreciated.
The thing to keep in mind about IMAP versus POP is that more folks
will be keeping things on your server. That means you're going to need
more disk space and (particularly if you use a Maildir backend) more
inodes, and you're going to want to reexamine your filesystem and
mount options. For example, if you haven't already, turn off atime
updating. It's entirely useless with Dovecot, and will just slow you
down.
~Kyle
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