Re: [dspam-users] postgresql and dspam

On Wed, Aug 03, 2005 at 12:37:18PM +1000, Michael Anthon wrote:
> On 8/2/05, Mike Horwath <drechsau@geeks.org> wrote:
> > One of the obvious things that people do with servers is give them a
> > lot of CPU and almost no RAM.
>
> Not all machines need a lot of RAM. Adding RAM if it isn't actually
> using any swap won't do anything except drain your wallet a little
> bit more.

Wow, that is a very interesting statement.

RAM in any modern UNIX type system is used to do a few things,
including caching of regular data from the filesystem, or in the case
of a database server, you can raise the usage limits of the DB server
process and gain a ton of speed.

It is all based on tunables.

Sure, you might not be using swap, but you might be starving your DB
server application.

> > Bring your RAM up.
> >
> > A lot of disk I/O means that something is very busy, more than likely,
> > you are hitting your VM system.
>
> You can easily test this hypothesis using a few simple system tools.
> I'd start with top and see how much RAM and swap this says is in
> use. The move to vmstat (e.g. "vmstat 2") to get some idea of what
> is actually going on with your system. This will soon tell you if
> you are thrashing swap or if something else is going on. In
> particular it should help you narrow down what the disk transactions
> really are

Thanks, but I now how to tune my systems. I am not the person who
might possibly be starving the DB server application.

I know more than just using 'vmstat' to look at things, there are a
ton of other tools available.

Trashing swap is something you don't need vmstat to check for...

To check on disk load, things like iostat do a better job. When you
hop on over to FreeBSD 5.x and above, you can run gstat as well, which
will give you a break down by mounted filesystem. Solaris can do
basically the same thing with iostat by using '-x' or '-xpt' on 9 and
above.

Why didn't you post to the list?

-- 
Mike Horwath, reachable via drechsau@Geeks.ORG