[Beowulf] Virtualization in head node ?

[Ashley Pittman]

On Mon, 2009-09-14 at 13:04 -0500, David Ramirez wrote:
> Still a newbie in HPC, in the first stages of building a Beowulf
> cluster (8 nodes). 
> 
> I wonder if anybody out there has used Linux virtual machines in the
> head node, just to be able to experiment with different configurations
> & deployments and jump back without much effort if things go bad. 

I do this all the time, I tend to run either a virtual frontend and N
virtual compute nodes locally on a server here or more commonly I just
start a number of Amazon EC2 instances as compute nodes and run the
frontend functionality on node zero.  For parallel jobs the compute
performance is dreadful (I over-commit the virtual CPU's) but for
experimenting and testing different setups it's ideal, I typically run
128 process jobs at a cost of $.40 per hour.  The software configuration
and deployment is exactly the same on virtual machines as it is on
physical machines unless you have any non-ethernet devices.

As for running production systems using Virtual machines, for the
front-end I'd be happy to do that as well, compute nodes should not be
considered for this however.

On medium sized clusters there is typically a "head node" which to run
the management software, the resource manager, and such and a second
front-end machine known as a "login node" for users to login to to
compile code, submit jobs and perform cluster I/O from.  On smaller
machines these two rolls are more often rolled into one machine.
Virtualisation allows you to separate out these two rolls again onto
separate VM's, if budget allows getting two physical machines and
running one Management VM and two Login VM's across them strikes me as a
good solution for providing resilience.  I'm sure a case could be made
for running ten Login instances here but I'm not sure of the benefits
myself.

Ashley Pittman.

-- 

Ashley Pittman, Bath, UK.

Padb - A parallel job inspection tool for cluster computing
http://padb.pittman.org.uk