[Dovecot] 1.0-test21

[Tom Allison]

Timo Sirainen wrote:
> On 21.6.2004, at 21:45, Moe Wibble wrote:
> 
>>> I recently saw some benchmarks (measuring system load) comparing
>>> Dovecot mbox, maildir and Cyrus. Dovecot was much slower than I
>>> thought, Cyrus was many times faster in most tests. Dovecot with mbox
>>> was also much faster than with maildir, even though my 0.99.10 mbox
>>> code is pretty bad.
>>
>>
>> Strange...  I'd think that rewriting the mbox files would cause a lot
>> more performance issues than shuffling around files in a Maildir.
> 
> 
> They probably were using mboxes that had already all the necessay X-UID 
> etc. fields, so rewriting wouldn't need to do more than really required.
> 
>>> 0.99.10 indexes aren't too good, but I still find it a bit strange that
>>> Cyrus takes something like 10x less load. I'd think most of it has to
>>> do with maildir format itself, that it needs to rename files when flags
>>> change, and Dovecot needs to resync the whole maildir after each change
>>> in mailbox (and sometimes twice).
>>
>>
>> I haven't tested dovecot in a high load (multiuser) environment yet
>> so I can't say much about the actual load in such a situation.
>> But once the indexes are made (and don't break) what's really
>> left to cause (unjustified) load?
> 
> 
> With maildir the problem is that once it's modified by Dovecot, I can't 
> know if someone else didn't modify it at the same time. So after I 
> change anything it, I'll have to resync the whole maildir again, just in 
> case.
> 

I get to ask a dumb question:
Can you put a filelock on the mail files while you are handling them to 
ensure that no one else is messing with them?
I guess the question is then, if you have N emails in folder, then how 
do you ensure that the other N-1 emails didn't get messed with, or that 
there aren't now N+m emails in the maildir...