[Dovecot] POP3 vs. IMAP Load/Memory usage in Dovecot 1.0.15

[lists at truthisfreedom.org.uk]

Hi all,

We've just provisioned a new cluster of dovecot nodes running Centos  
and Dovecot 1.0.15 (we needed to match the original configuration,  
we're upgrading to 1.2 next week!).

The nodes are currently equally allocated (50/50 split) to IMAP and  
POP3, with the intention to move them into a single cluster hosting  
both services in the next month.

All the servers are of identical spec (24 cores, 24G RAM) and are  
configured to load the indices, control files and maildirs via NFS.

We have noticed that the IMAP servers appear to be under much less  
load and utilising drastically less RAM than the POP3 servers and I'm  
wondering if there is a reason for this as we have seen some swapping  
onto disk yet we are only handling 500 concurrent POP3 connections to  
each server at any given time compared with over 600 IMAP connections.

I'm wondering if we've missed a config flag somewhere or (better  
still!) this issue will go away when we upgrade to 1.2.

If anyone can shed any light on this, that would be much appreciated.

Thanks in advance,

Matt