[Beowulf] Application Deployment

Mark Hahn hahn at physics.mcmaster.ca
Sun Oct 10 11:43:11 EDT 2004


> RPMs or Debian.  With Red Hat and descendents (Fedora, Centos) you can
> use kickstart, which is a lovely tool for installing clusters.
> Kickstart run on top of PXE and DHCP makes installing most systems a
> matter of turning them on (after making a single host specific MAC

don't forget the zero-install approach - nothing installed on nodes.
just export the nodes' root filesystem from a fileserver, and you never
have to do anything per-node.  yum and rpm both let you install within
a separate tree, so the fileserver doesn't need to be running the same 
config as the nodes.

obviously, this results in a certain amount of NFS traffic, as opposed 
to having those files installed on the node's disk.  issues:

	- diskless nodes are very attractive in many contexts:
	reliability, price, maintainability, etc.

	- running NFS-root is a way of tolerating local disk faults;
	lack of swap may or may not be a problem.

	- NFS can easily be faster than local disk IO.

	- in aggregate, a buch of diskless nodes will, in the worst case,
	create much more traffic than your net and fileserver can handle.

	- my experience so far with 50-100-node clusters is that a 
	single NFS-connected fileserver is actually pretty good.
	(our nodes have a local disk used for things like checkpoints
	of big parallel applications.)

	- for big MPI clusters, it's extremely attractive to put
	fileservers directly onto the MPI fabric.  suddenly, gigabit
	is no longer a limiter for file IO and systems like Lustre
	can give some pretty impressive data rates.

	- this scheme is probably optimal for very hetrogenous 
	datacenters as well, where you might boot a node in some 
	random OS purely for a particular user/app.  that kind of thing
	seems very dubious to me, but it would only take a few minutes
	of perl scripting to write a web frontend to select things 
	like IP, distro, kernel, server, etc for a particular node,
	and propogate the changes.

I think that for a small cluster, I'd consider having the nodes
with full installs on them.  for anything larger than say 4 nodes, 
I definitely prefer the root-on-fileserver approach with "ephemeral" nodes.
it's also pretty sexy to take a node out of the box, plug it in and have it 
accept jobs in a minute or so with no manual intervention.

> course, require knowledge, experience, wisdom, and time to do right,
> which is why sysadmins get paid and are worth a very decent salary.

hmm.  anyone for a cluster-admin salary survey?

regards, mark hahn.

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