[imp] Re: Hack concept - IMAP speedup

Ross Becker ross at rbecker.org
Wed Sep 8 15:35:30 PDT 2004

I just got an email and went to look. I see two issues.

1. It does not contain an MDA- So when does it update the indexes after 

2. It doesn't support maildir++ and quotas. I need quotas.

It might be less work to add quotas to dovecot then add indexes to 
courier, though. I've just never heard of this IMAP server before now, 
so I'm not sure how widely used it is.  I searched for IMAP servers at 
www.imap.org too.  I'm guessing dovecot is pretty new?


Paul Reilly wrote:
> Look at Dovecot IMAP - www.dovecot.org
> We switched from Courier to Dovecot and noticed a huge performance
> boost. Mainly because it keeps indexes.
> Paul
> On Wed, 8 Sep 2004, Ross Becker wrote:
>>Just throwing this out, I'm really not certain as to which organizations
>>I should be talking to about this, but Horde/IMP seems as good as any.
>>Currently, free IMAP servers which are capable of webmail backend is bad
>>for any organization which can allow large folders. The primary reason
>>is that maildir (and maildir++) has no indexing at all. This means that
>>to sort a folder, you have to open every message, read the headers, suck
>>out the one(s) you need, and transform them into sortable format.  Once
>>you've read every message, then you can sort.  This leads to woeful
>>performance.  On a Pentium 4 with 800mhz memory bus, I clocked
>>Courier-IMAP taking ~14 seconds to sort a 12.5k message folder by date.
>>Clearly, for a webmail system, you want the server to be able to sort
>>the messages fast, because all sorts will happen on the server.
>>I'm looking at hacking (probably) procmail, and Courier-IMAP to maintain
>>  fixed-length record files containing the message headers needed to
>>support standard search and sort operations.  Not indexes, as that would
>>require putting sorting code into the MDA (procmail).  At a wild guess,
>>  this should provide at least an order of magnitude improvement in
>>search and sort times.
>>The ugliness is figuring out if procmail is the best delivery agent to
>>add this hack to (I'm leaning there because of it's excellent support
>>for delivery recipes & filters) and if there's any way this could be
>>done in such a fashion that it could go into permanent project code.
>>If anyone else here is interested in this hack, has thoughts, or
>>whatever- I'm all ears.
>>    Ross
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