Hardware: Single Quad-Core processor 2.5 Ghz

OS Platform: RHEL 4 update 5

I/O bond apps/servers: SMTP(sendmail), NFS, SAMBA
I/O and CPU bond apps/server: Database(Oralce 10g R2)

Requirement: Optimum performance

a, what should be the max value of context switching (cs) ?
b, what should be the max value of Time spent waiting for IO (wa) ?

esp how do I know the reason behind the high value of wa,
i.e, is it because the high network I/O or high disk I/O

I know the high value of 'bi' and 'bo'(disk I/O) is also the cause of high value of 'wa', but how do I know that if the high rate of network I/O is also involved in the high vlaues of 'wa'

I mean how can I check that too much network I/O or slow network is also involved in the high value of 'wa'