[Dovecot] Dovecot and SSD

Chris Hoogendyk hoogendyk at bio.umass.edu
Fri Jul 30 15:54:25 EEST 2010

Bryan Vyhmeister wrote:
> On Thu, Jul 29, 2010 at 9:57 PM, Chris Hoogendyk
> <hoogendyk at bio.umass.edu> wrote:
>> Curtis Maloney wrote:
>>> Umm... apart from "shiney toys", is there any legitemate reason for such
>>> expense on performance tuning?
>>> I ask because we have about 30 users using our IMAP server (Dovecot 1.1),
>>> which also serves as our main Samba server, and until recently was also a
>>> CUPS server.
>>> This on a Sun V100 ( 450MHz UltraSPARC-IIi ) with 1G RAM and two dull,
>>> standard IDE HDDs ( a 40GB for OS and mail, and a 320GB for Samba).
>> I was going to bring up something like that, but I wasn't sure it was fair
>> comparing my server.
>> I do not have SSD's. But, I have a larger user base and I have a Sun T5220,
>> which is 8 core, 8 threads per core, etc. The drives are 15Krpm SAS. Using
>> Sendmail, mimedefang, Dovecot, Squirrelmail, etc. Also running Apache2 with
>> Drupal, MySQL, gene sequencing apps, PostgreSQL, Samba for file sharing and
>> printer spooling, as well as some other stuff. Squirrelmail/Dovecot is
>> virtually instantaneous even with very large mbox format inboxes.
>> Thunderbird mail checks via Dovecot are also virtually instantaneous. I have
>> over 1500 accounts on the system, although probably only a few hundred are
>> very active. Granted, it is summer, and things will pick up in the Fall, but
>> I doubt it will push this server too much.
> I do understand where both of you are coming from completely. I have
> also run a similar setup as the Sun Fire V100 with a Sun Fire V120 and
> it performed beautifully. There are two main scenarios where using an
> SSD is interesting to me. Both scenarios involve using a Mac mini.

Nothing against SSD's.

Where are we coming from?

Well I guess we were both thinking in terms of general ideas of system 
tuning -- looking at a system from the perspective of all the components 
and trying to see where the limiting factors are. The interesting thing 
about the T5220 is that the clock speed is less than half what most 
Intel based servers are these days, but it is highly tuned for a 
multi-threaded web2 type environment. As well as 8 core and 8 threads 
per core, it has 8 encryption accelerators for all those ssl 
connections. Throw a huge load of web and mail transactions at it, and 
it outperforms the competition. We have an example of an 8 core AMD 
based system that is virtually new, purchased to be a multi-department 
web server, and our T5220 is noticeably faster carrying a heavier load. 
That's tuning. However, if we had non-threaded, compute intensive 
applications, the scales would tip the other way.

 From that perspective, I don't see anything wrong with a Mac mini for a 
small group of users. But, if cost is an issue, I think I would be 
trying to get a better tuned custom Intel or AMD box for the money, 
rather than adding an SSD to a Mac mini. Multi-core cpu's are becoming 
pretty standard. Adding memory is a big item. Faster disk drives in 
general can make a difference -- compare all the options. Look at the 
bus structure and the general i/o capabilities. Although I'm the primary 
Solaris admin, we've been using Ubuntu for more and more things. It 
performs quite well. All of those things get juggled together when 
choosing a system and deciding how to set it up and tune it.

There's certainly nothing wrong with experimenting and playing with 
these things, as long as you can do it without stressing out your budget.


Chris Hoogendyk

   O__  ---- Systems Administrator
  c/ /'_ --- Biology & Geology Departments
 (*) \(*) -- 140 Morrill Science Center
~~~~~~~~~~ - University of Massachusetts, Amherst 

<hoogendyk at bio.umass.edu>


Erdös 4

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