Need to find a bottleneck when traffic is kinda high

Hello there all,

i have one page that uses periodically_call_remote to update about 65
divs on this page every 5 minutes or so. The page also uses a rather
large background map.

the server we are using has 4 cpu at 2ghz, 8meg RAM and 5 disc RAID 5.
our connection is 1.5 meg upload.

we seem to really get bogged down on high traffic times. I have
watched gkrellm, and it doesn’t seem to be the processors or RAM that
is limiting anything.

Other php sites hosted on the main server here (virtual hosts in
apache) also slow down considerably.

i am using rails in production mode, fastcgi.

What kind of tool would you guys reccomend that i use to determine
what my bottleneck is ?

could it be disc? i have tried to optimize my tables and indexes, but
can’t really tell what our limiting factor to speed things up here is.

Is ajax expensive on the server?

thanks for any tips.