[H-GEN] How big should the paging partition be?

[Ewan Edwards]

I'm sure this is one of those questions that will bring out many and 
varied opinions, so I apologise in advance to those who don't 
necessarily want to see that much email traffic.

On with the details of the question ... 

I am about to install RHEL5 x86_64 on three IBM x3650 servers.  They 
each have two dual core Xeon processors and 17Gbyte RAM.  (That's 
correct seventeen GByte, it's not a typo.)  These machines will be 
used as virtual machine hosts using, primarily, VMware Server.  

To work out a paging partition size in the past, I do a rough estimate 
of the memory requirements of all the programs likely to be running 
at the same time, subtract the physical RAM and add 32MByte.  

More recently, I've just allocated twice the physical RAM.  This is 
only because I read that the paging algorithm employed by the 2.4 
Linux kernel can cause the page space to become fragmented if the 
page space was less than twice the RAM size.  I don't know if this is 
still valid in the 2.6 kernel.

In any case, it seems a little excessive to allocate 34GByte (=2x17) 
to a paging partition.

Any suggestions?