Questions on Cyrus IMAP

Jules Agee julesa at
Mon Mar 28 20:23:23 EST 2005

gopalakrishnan kamalanathan wrote:
> Hi,
> I have a few question on the Cyrus IMAP implementation.
> 1) What is the memory footprint of the Cyrus IMAP.
This will vary with usage, more concurrent connections will require more 
RAM. An anecdotal sample from my server shows:
imap process: resident set size 1996k of which 1620k is shared
lmtp process: rss = 1640K with 1360K shared

> 2) What is the maximum number of simultaneous connections that the Cyrus 
> IMAP server can handle.
I don't know what the hard limits are, if any. In practice, it will 
depend on available RAM and other system limitations. I believe the CMU 
folks regularly see around 15000 concurrent connections, though that's 
spread across eight or ten Cyrus servers, if I remember correctly.

> 3) How many threads does the Cyrus imap server create?  Does it have a 
> fixed pool of threads or does it create new threads as and when needed 
> basis?
It's not threaded. It keeps a pool of processes waiting for connections. 
  The number of pre-spawned processes is configurable. As they are used, 
new processes are spawned and added to the pool.

> 4) Is it possible to have multiple connections to the same mailbox?
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