[Beowulf] first cluster

[Douglas Guptill]

Hello Gus:

On Mon, Jul 12, 2010 at 03:02:40PM -0400, Gus Correa wrote:
> 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.

We have bought enough RAM (6 GB /core) that will I hope prevent swapping.

> B) input/output data files that your application programs may require
> (if they already work in stagein-stageout mode,

Now there you have me.  What is stagein-stageout?

> 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).

I am hoping to do that - write to local disk.  Each node has a 1 TB
disk, which I would like to split between the OS and user space.  How
to do that is still an unsolved problem at this point.  The head node
will have (6) 2 TB disks.

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

Good question.  The node count is 16 (not 124, as I said previously -
brain fart - 124 is the core count), and seems to me just over the
border of what can be easily maintained as separate, diskful installs.
Our one user has expressed a preference for "refreshing" the nodes
before a job runs.  By that, he means re-install the operating system.

> 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?

I like that idea.

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

I looked in the beowulf archives, and only found very old (+years)
articles.  Is there another archive I should be looking at?

> Just some thoughts.

Much appreciated,
Douglas.
-- 
  Douglas Guptill                       voice: 902-461-9749
  Research Assistant, LSC 4640          email: douglas.guptill at dal.ca
  Oceanography Department               fax:   902-494-3877
  Dalhousie University
  Halifax, NS, B3H 4J1, Canada