Server Load High (I/O)

[arazas]

Due to high IO load server is going crash once a day.

I have optimized the MySQL, Upgraded the kernel but still it's same. The SWAP seems normal.

Now probably it is due to high traffic of http or emails. How should I diagnose and fix it? I am in big trouble.

Its PIV 3.0, 1GB Ram and 450 Websites