A quick and easy performance improvement
rich at mail.wvnet.edu
Wed Jul 26 14:30:42 IST 2006
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!
Making the change is trivial (from root)....
1. Shutdown MS
2. mkdir /var/spool/spamassassin
3. mv .spamassassin/bayes* /var/spool/spamassassin/
4. Edit /etc/MailScanner/spam.assassin.prefs.conf and uncomment the
lines which define where the bayes DB is located. Thanks Julian!
5. Start MS
Just wanted to let others know and perhaps benefit from our experiences.
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