Simon Gray wrote:
> Michael Monnerie wrote:
>   
>> Note:
>> Everybody who care about their data, you should leave this setting on 
>> it's default "1":
>> innodb_flush_log_at_trx_commit=1
>>   
>>     
> Also, this will only affect writes - rather than reads.
>
>   
If you have minimal writes and the server is on a UPS, this setting 
won't make too much difference, but if you have a lot of messages coming 
in, then a setting of 1 would be safer, but further reduce read 
performance under a mixed load. Moving towards 2.3.x should lend some 
speed increases depending on what searching you are doing. If you are 
searching single folders, then reducing the number of messages in each 
folder will help speed it up. Moving messages by date received to a 
sub-folder of year, quarter, or month can make a big difference. Bigger 
mailing lists I use by month "2009-09_Sep" to keep the message count < 
10k per folder.

I agree that the majority of your problems lie in disk i/o bandwidth. 
Use a good hardware raid 10 (not a fake hardware raid that is really 
software aka promise sata) with disks that have low seek times, a larger 
on disk buffer, and good sustained read throughputs. You should never 
use a raid5 for a database as the write performance will be very poor 
when writing out data that is less than the stripe size, causing all 
disks to be read, computed, then written to the affected disks. I use a 
3ware 9650SE-4LPML, with 4 SATA 1 disks in raid 10. My database is only 
20GB though and I have 6.5 GB of ram on mysqld. I'm planning on 
replacing the disks with some SATA 2 drives in the future, but just 
haven't procured them yet. I have about 550K messages right now in the 
database spread over 10 users, my account being the largest. With 2.3.x 
my database is about 2x the amount of mail stored, which is an 
improvement over 2.2.x.

You might also check into OS level tweaks for your disks to get every 
last bit out of them and the controller.

-Jon

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