[Beowulf] first cluster

Gus Correa gus at ldeo.columbia.edu
Mon Jul 12 12:02:40 PDT 2010

Hi Doug

Consider disk for:

A) swap space (say, if the user programs are large,
or you can't buy a lot of RAM, etc);
I wonder if swapping over NFS would be efficient for HPC.
Disk may be a simple and cost effective solution.

B) input/output data files that your application programs may require
(if they already work in stagein-stageout mode,
or if they do I/O so often that a NFS mounted file system
may get overwhelmed, hence reading/writing on local disk may be preferred).

C) Would diskless scaling be a real big advantage for
a small/medium size cluster, say up to ~200 nodes?

D) Most current node chassis have hot-swappable disks, not hard to 
replace, in case of failure.

E) booting when the NFS root server is not reachable

Disks don't prevent one to keep a single image and distribute
it consistently across nodes, do they?

In any case, I suppose you could both have disks and boot with NFS root.
But if you have disks, is there really a point in doing so?

I guess there are old threads about this in the list archives.

Just some thoughts.

Gus Correa

Douglas Guptill wrote:
> Ah Ha.  I see the point of a non-diskful, or nfs root, install for the
> compute nodes.  One image to update/change, instead of a whole bunch.
> Thanks,
> Douglas.
> On Fri, Jul 09, 2010 at 07:11:18PM -0400, Mark Hahn wrote:
>> well, the thing about nfs root is that there's almost no installation,
>> per se.  if you wanted, you could boot the nodes off a live master's  
>> root filesystem.  normally, master and node images are kept mostly
>> separate, though, because it's handy to avoid entangling them
>> (ie, you may not want mysql-server installed on compute nodes, but only 
>> on the master, etc.  or just different versions.)
> And from Steve Crusan:
>> As for the diskfull install, netbooting and statelite (NFS root) solutions
>> are very easy to scale and customize. Diskfull installs seem to be less
>> flexible in IMO.

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