A quick and easy performance improvement
dave.list at pixelhammer.com
Wed Jul 26 19:20:13 IST 2006
Richard Lynch wrote:
> Julian Field wrote:
>> 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 can't see why it would either. If you're using one large partition
> changing the directory structure wouldn't be worth anything as far as
> performance goes. In my case they are on different partitions.
>> 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.
Maybe I am showing my ignorance but how? I'm not seeing any performance
issues myself, just curious. I currently have bayes on one
controller/disk pair and the queues on another controller/disk pair.
I've always believed that to be about the best you could do.
Of course it just takes 2 minutes in a terminal if I should move bayes
to the same controller/disk as the queues.
> I think you're right. Is it uncommon to have / and /var on different
> partitions? The sysadmins here argue for separate partitions because
> it lessons the likely hood of the rootfs filling up. They say that it
> can hose your system to the point that you can't even logon to fix it.
> So, we split / and /var (and others). I think all of our unix systems
> are that way. Is this a bad practice?
> -- Rich
I have always used separate partitions, though others who do as well
have told me I am stupid because I use different partitions than they
do, everyone has an opinion ;^)
I keep separate partitions for the sake of fsck, performance be damned.
I've lost data on the far side of a 70gb disk because I had a failure
fsck couldn't fix, (SATA drives and a sad story). I've isolated /, /tmp,
/var, /usr, /data ever since. I keep websites, backups, ftp directories,
mail queues, etc in /data. Depending on the task the server is doing.
Three years now I've asked Google why they don't have a
logo change for Memorial Day. Why do they choose to do logos
for other non-international holidays, but nothing for
Maybe they forgot who made that choice possible.
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