Server hardware specification php application

[knowj]

We are looking at developing an online php website/application that is expected to have around 200,000 users. The thing I am currently finding hard to come by is any documentation relating to hardware/environment/load on what sort of specification server we would need to be looking at to handle this sort of traffic.

Is there a basic formula that you can work to work out hardware specifications based on load?

Basically don't want the server to die under peak load or if a campaign is run.

Cheers
J

[sneakyimp]

It's nearly impossible to say what kind of hardware you need without considering all kinds of details. How often do your visitors access the site? How many pages do they click in a given time frame? Etc.

I am a developer for a site with approximately 100,000 registered users. Our LAMP box serves about 90,000 PHP page requests a day with no problems. A given page request might have anywhere between 5 and 20 database queries to a mysql database. The machine also handles email, DNS, spam filtering, and virus scans for a handful of email accounts (just our employees and forum notifications).

The machine's hardware:
CPU: AMD Athlon 64 X2 dual-core 2.2GHz
Memory: 1GB (i think it runs at 667 or 800MHz)
3 hard drives:
one for boot, /var, /tmp, /home
one for /backup
* one for mysql files

Peak traffic is pretty much happening as I write this. 'uptime' shows a pretty low cpu load:

[user@server ~]# uptime
 13:09:54 up 146 days, 20:53,  1 user,  load average: 0.40, 0.24, 0.20

Once you have a machine running your site, you can use apache bench to test it.