Performance Problems.. Server hardware smoked by $500 box?

[Marc Slemko]

On Thu, 11 Sep 2003, John Straiton wrote:

> Greets!
>
> I'm pretty confused right now with trying to determine the nature of a
> performance problem I'm having on one of my servers. The server is a
> webserver with a separate db/file server sitting behind it. The issue is
> that in pulling up websites from the machine, my silly POS development
> box has nearly double performance although one would think it shouldn't.

you need to quantify the performance differences starting with
replicating what you see, and work down from there.

Do the differences in the numbers you posted mean anything?  No
idea.  I wouldn't expect them to make any difference for a single
user hitting the server, but it is possible they are related to
some problem somewhere.

The easiest way to tell, however, is to start with the problem you
do see (ie. things are slow loading) and work down through the software
stack from there.

The first step would be to try to quantify the performance
difference in serving the actual web pages.  Find a single page
that you think is slow on the production system and that can be
accessed without having to be part of a session, and quantify the
performance difference for that page.  Remember you don't care about
high load, just a single user request.  You could use apachebench
("ab", comes with apache... something like "ab -c 1 -n 20
http://server/path/to/page") or any simple command line tool that
you can time (eg. repeatedly run "time GET http://server/path/to/page").
Do this from as near as possible to the box you are running the
web browser that sees the slowness loading.

Until you can reproduce and quantify a performance difference at
this level, don't worry about digging deeper.

Once you can, keep taking one step closer.  Try requesting a page
that doesn't hit the database.  Try setting things up so NFS isn't
being used.  Try making the request from the same machine the web
server is running on.  etc.  Your goal here is to eliminate as many
components as possible while still being able to reproduce the
high level problem.  So, for example, if you can reproduce it on a page
that doesn't hit the database... you can eliminate that from further
consideration.

Unless your application is extremely heavyweight and demanding on
hardware, or there is some bug in one of the drivers or configuration,
none of the hardware differences would normally have any effect on the
symptoms you say you are seeing.