Apache Concurrent Users for a PHP/MySQL website?

Question

I am building a website that is developed in PHP and relies heavily on database. I am expecting upwards of 1000 users on at any given time.

Having done some tests using ab in a virtual system with 512 mb ram, I found the website will fall over after roughly 75-100 concurrent users. The performance does start to trail off prior to this but its within an acceptable limit.

What I am wondering is what kind of setup should I have for a practical website. I am expecting allot of people on the website at the same time and I want to be able to give them a reasonable level of service. As a result, I am stumped about what kind of server setup to have for this.

Currently looking at a really powerful quad core machine with 8gb of memory. This should provide me with enough memory for these users, but I am still concerned about the overall performance/response time I would get form this setup.

Someone suggested that it might be better to have two less powerful machines, one for MySQL and one for the php/apache - as my website is database intensive.

Anyone out there with a bit more knowledge on this kind of deployment, that can help me out with some guidelines/info on what would be a better setup? Obviously I don't want to pay too much for the setup either, so it has to be cost effective also.

Answer 1

Make sure the drives you use have the fastest access speed you can get, preferably in a redundant RAID array.  You should also be able to hot-swap them.

Quad core is good, redundancy is essential for such high traffic.

Use multiple internet connections if possible.

If you choose to use a second machine you will need an extremely high speed data link between them.  It may be best to concentrate on a single, extremely reliable machine.

Remember, multi-threading is your friend!  I believe it is possible to run multiple instances of the PHP parser, possibly also the Apache daemon.