Linux Performance Tuning

Dear Managers,
I am looking into enhancing some o the linux machines, i have already
run sar on them to collect some data, and was wondering what
information is out there to make the systems perform better they are
data crunchers, that use large sets of data, so /proc/sys/kernel/shm*
are one of my targets, but looking around for the best setting for
this i have found the following on an old perf. tuning tool vtad  "By
looking at /proc/sys/kernel/shmmax and comparing it to the first entry
in /proc/meminfo/Mem (physical memory), we can see the shared memory
       limit as a percentage of physical memory. VTad recommends
allowing at least 10% of physical memory to be shared, and prefers
25%. This helps Apache to cache files, if that feature is enabled"
well one admin told me its always  better to set it up to the same as
physical memory as it will not hurt, and i tend to agree with him, so
my question are the following :
1- how many people use VTad?
2- I have found another tool similar to VTad,  called sarcheck, are
there any other tools beside the three mention here in my mail to
suggest performance tuning parameters?

the Linux boxes i am talking about do heavy data crunching, and
network I/O, are there any  good books about the subject ?

I will summarize given time, and responses of course :)

TIA
good day,

Jawal
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