Debian Good for Clustering?

[Bob Freemer <bob.freemer@medomics.com>]

I remember reading somewhere an apt-gettable or debian-specific project 
for clustering.  Rolling my own from openmosix is a pain.

The CPU clustering is easy with the right kernel recompile, but I would 
like to use the hard disks on multiple machines on the network as 
something akin to a RAID-5 array, and have one large, redundant mount 
available.  This is part of some experimental medical systems trials, 
and may have up to 10's or 100's of machines, each with 40+ GB hard 
disks.  A user-mode application should automatically rebuild/resize the 
array if a given machine went down or was powered off.

Does anyone know of any projects to do this?  A focus on Debian and 
apt-gettable packages strongly preferred!

Bob