[Dovecot] Performance, dovecot vs tpop3d

[Nate]

At 09:01 PM 1/30/2007, Curtis Maloney wrote:
>Nate wrote:
>>Perhaps another test i'll run, just to compare apples to apples 
>>tomorrow would be to use a memory index with dovecot as well, and 
>>see if that drops the I/O load to the same as when tpop3d is running.
>
>Speaking of "Apples to Apples", you might want to try with 
>INDEX=MEMORY on Dovecot, see how that fares.
>
>If your users are only POP3 and download all messages at once, not 
>keeping mail on the server, you can (iirc) disable indexing 
>altogether, since it's a wasted effort.

That test was on my list to try out today.  I ran the test, and 
performance was severely degraded.  Upon every new login, the entire 
index was rebuilt.  So with any login it takes the full ~30 seconds 
to rebuild the index on a 17000 email user.

I've confirmed also that tpop3d is doing no indexing whatsoever on 
disk.  It isn't even compiled with that option.  So it seems it is 
probably disk caching which is assisting tpop3d with returning a 2nd 
login (within a few minutes) so quickly.

I wish it were the case that all users downloaded messages, but it 
seems all too often users click the 'leave messages on server', and 
never expire them.  We have quite a few users (thousands probably) in 
that condition.  We occasionally delete old stuff.  Did I hear about 
an expire plugin upcoming?  That would be useful.

- Nate