A quick and easy performance improvement

[Julian Field]

Richard Lynch wrote:
> uxbod wrote:
> 
>> Why not hold the bayes on a RAM partition, and have a cronjob that 
>> periodically backs it up throughout the day so that changes are not 
>> lost if the server crashes ?
>>  
>>
> 
> That would definitely improve things.  Seek time in RAM is zero!
> 
> While monitoring disk I/Os (iostat 1) I was surprised at the high number 
> for bayes.  I didn't expect to see it so high.  One my systems it was 
> actually higher than the I/O for the mail queues.

That's very interesting.

Most people these days just use 1 big partition for / and nothing else. 
So it won't be available to them. So why is this an improvement when 
/var/spool and /.spamassassin are on the same partition? I can see why, 
if they are on different partitions, though you're still relying on the 
mapping of sector number --> physical hard disk location. But if / and 
/var/spool are on the same partition anyway, why would it run any faster?

I am sorely tempted to say that you have merely cancelled out the speed 
slowdown caused by splitting / and /var onto different partitions. If 
they are both on the same partition anyway, and are being written to a 
lot, they will end up very close to each other by virtue of how the 
filesystem is likely to work.

I think that splitting / and /var slowed your system down. You have just 
cancelled that out.

Thoughts?

> 
> -- Rich
> 
>> On Wed, 26 Jul 2006 11:21:57 -0400, Richard Lynch 
>> <rich at mail.wvnet.edu> wrote:
>>  
>>
>>> Nathan Olson wrote:
>>>
>>>   
>>>> Would noatime affect bayes operation on /var/spool?
>>>>
>>>> Nate
>>>>
>>>>     
>>> Noatime will probably help since it would reduce the number of I/O
>>> operations to the disk -- fewer I/Os is good for performance.  If I
>>> recall correctly, noatime means that the system will not update the last
>>> access date for the file.  One less I/O will certainly help.  The
>>> benefit I'm going after comes from reducing disk seek time by putting
>>> the bayes DB closer to the mail queues.  For me, using pretty much a
>>> default installation, the benefit was in decreasing the IOWait time to
>>> 1/10th that value it was.
>>>
>>> -- Rich
>>>
>>> -- 
>>>
>>>
>>>
>>>
>>>   
>>
>>
>>  
>>
> 
> 

-- 
Julian Field
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