[Beowulf] Nodes with or without HD?

Jag agrajag at dragaera.net
Wed Jan 14 12:58:38 EST 2004


On Wed, 2004-01-14 at 12:36, Mathias Brito wrote:
> I would like to know how better or worse is a cluster
> with nodes that have HD. All my nodes in my cluster
> have HD with the System installed. I cannot see why it
> could be worse. Well if anyone have the answer, please
> answer.

There are plus and minuses.  If you are not familiar with what it takes
to admin a bunch of machines and keep them all in sync together
(probablly using something like yum), then you may find it easier to
have diskless nodes all sharing a single /usr over NFS so that its
easier to update software.  Likewise, diskless nodes can be quicker to
add to the cluster, however if you're using kickstart and have a good
kickstart config setup, nodes with disks aren't that hard to setup
either.

On the other side.. diskless machines require more network load in
general.  Unless it happens to be cached, whenever you need to access a
file, you have to hit the network.  This causes network congestion that
can slow down MPI and such.  It also means that it takes the slave node
wanting the file longer to read it.  So it can be quite a performance
hit.  But that also depends on what your networking needs are based on
what kind of networking you have.

Note, when you said diskless, I assumed you're talking about using
NFS-root.  If you're using Scyld, then things are a bit different. 
Their system of diskless slave nodes is a lot different.

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