imap server performance benchmarks

[Bill Campbell]

On Fri, Mar 09, 2012, Da Rock wrote:
> I'm reconsidering my current setup (postfix/courier) for imap and I was  
> doing some research on performance comparisons between imap server  
> setups. I stumbled on this article just just about fell of my chair  
> laughing when I read the last article on future benchmarking tests to  
> perform:
>
> research.microsoft.com/pubs/138302/lisa.pdf
>
> Considering I have close to a hundred folders or more, and an average of  
> 50,000 emails in each (yes, not good, and I am working on archiving but  
> it won't help _that_ much) with nearly 200,000 in just one! I got a real  
> kick out of the comment that "no sane email user would have more than  
> 21,000 emails in a folder" - that would make me certifiable :D Oh, and  
> that most email wouldn't be more than a GB or so... mine's edging 6GB  
> already...

My security folder averages about 19,000 messages, containing all security
reports for the last 30 days (it's a bit over 22,000 today).

> So, all jokes aside, I contemplated that I would make an ideal test case  
> to the extreme for benchmarking imap servers. Anyone have any  
> suggestions on what to test/how? Anyone have some tools they have  
> created for a similar challenge? I have my own ideas, but if anyone  
> wants me to try something I'd be willing to give it a shot.

We have been using courier-imap for at least a decade including
at several regional ISPs with 10,000 accounts or so.  This has
worked very well with minimal problems.

During this time we have had to move all e-mail accounts to new
servers, and this has been pretty simple.  Set up the accounts
and $HOME directories on the new machine.  Change the DNS to
point to it. Then copy all the data from the old box to the new
using rsync.  This would take a couple of hours with 10,000
accounts.  During this time all new mail was processed and
available immediately while older messages weren't until the
rsync jobs were complete.

When we first started building systems for ISPs in 1994, we were
using the University of Washington IMAP server, and had a variety
of problems as systems grew.  Its monolithic file storage
required special handling, and I learned about inetd limits on
handling large numbers of incoming connections the hard way.

I much prefer the Maildir stores as they allow use of standard
*nix utilities, find, grep, etc., are hard to corrupt, and have
no locking problems with NFS mounts.

The courier method of having multiple authentication processes
has held up very well over the years under heavy usage.

Bill
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