[Beowulf] SLC3

[Mark Hahn]

> And if we want to upgrade the software (like MPI libs, c libs, etc.), we want 
> to do it real fast.
> 
> What's the best bet?

don't install anything on the nodes.  booting over the net (dhcp/tftp/pxe)
works extremely well, and means that upgrading a package for all nodes 
takes exactly one serial rpm/yum invocation on the fileserver.

I don't even bother with initrd's - just deliver a monolithic kernel
to the compute nodes and have them mount their root over NFS.  remember:
other than init and something like sshd, the boot sequence for a compute
node can be very abbreviated, not a lot of file IO.

just because the nodes are ephemeral (nothing installed) doesn't mean 
that you can't use the disk on a node if it has one.  it's great for 
swap and /scratch.