Slow Database

[Dominic Hayhoe]

My site uses mysql 5 and when I have 300 people or more querying the database the site slows down to a crawl. It's definately the db doing it as its maxing out the cpu and when i switch off the db the site springs to life again.

Here is a list of my db parameters is there anything I can improve?

MyIsam Parameters:
Advanced Settings:
Extra Sort File Size: 100k
Max Sort File Size: 100k
Myisam sort buffer: 150mb
(everything else greyed out)

Innodb Parameters:
Buffer Pool Size 64MB
Add. mem Pool SIze 16mb
Log file size: 10mb
Log buffer size: 1mb
thread concurrency: 8


Performance:
Cache Size: 100MB
(everything else greyed out)

Networking:
Max connections: 100
(everything else greyed out)

Advanced:
Thread Cache Size: 8
Read Buffer size: 64k
Read Rnd Buffer size: 264k
Table Cache: 256
Temp Table size: 103mb
(everything else greyed out)

Query Cache hitrate when I just looked with only 50 people using the site was at approx 80%.

I have 3 gig of memory and 2x2.4 gig Xeons


Is there anything in system variables it might help if I post here?

Thanks a lot.

Dom.