A quick and easy performance improvement

Richard Lynch rich at mail.wvnet.edu
Wed Jul 26 16:00:01 IST 2006

denis at croombs.org wrote:

>>I thought I'd post to the list about a change I made yesterday which
>>provided a huge boost in system's performance.
>>By far the largest amount of time spent in the life of a disk I/O
>>operation is seek time.  Seek time is the amount of time it takes to
>>move the disk R/W heads from one cylinder to another.  The /var/spool
>>filesystem is where the inbound and outbound mail queues are located.
>>Note also that the Bayes database is accessed heavily when analyzing a
>>Like many installations we have our root filesystem (/) and /var
>>filesystem on separate partitions on a single hard drive.  The default
>>location for the SpamAssassin bayes database is in /root/.spamassassin/
>>which is on the rootfs.   Moving the bayes database to
>>/var/spool/spamassassin resulted in a huge decrease in IOWait time.  In
>>our case it was an order of magnitude reduction.  For example,  IOWait
>>percentages went from 30% to 3%.  IOWait is the percentage of time the
>>processor is waiting on an I/O operation to complete.  Our mail queues
>>no longer get behind and throughput is outstanding!
>I would also assume having them on different hard drives would give an
>even larger increase in throughput ?
Most certainly, however this would depend on what else is happening on 
the two drives. 

-- Rich


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