IMAP sync tool (rsync for IMAP)

Marten Lehmann lehmann at
Mon Dec 25 19:56:13 EST 2006


> Downside: If you have very large messages on the source IMAP servers, 
> you better run the script on a machine with lots of RAM. On my system it 
> died repeatedly with "out of memory" when it was hitting a 32MB message 
> (on-disk size), and the system has 1GB RAM.

strange, I didn't experience this while running a sync for >15.000 
mailboxes some weeks ago with even larger messages partially.

> It's probably best to run it on a 3rd system, one that's separate from 
> both the source and the destination IMAP servers, otherwise unpleasant 
> things might happen if the script starts to gobble up RAM on the IMAP 
> server. Again, this 3rd system is best if it has lots of RAM if you 
> allow large messages on your source IMAP server.

Thats surely a good advice, but I don't think it is primarily because of 
the memory usage, but because of the CPU usage. While syncing and 
checking for differences on source and target server imapsync will use 
_much_ CPU ressources, especially if you are running several instances 
of imapsync at the same time to speed up the sync (on different 
mailboxes of course). The source and target IMAP servers have been 
pretty idle while the 3rd server running imasync had a load average of >50.


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