[Beowulf] Should I go for diskless or not?

Douglas Eadline deadline at eadline.org
Fri May 15 08:26:36 EDT 2009


You will note that I used sufficient wiggle words "usually" and
"generally" because in my experience it always depends.
And of course my comments are from my personal
experience. I have found that diskless allows for
the entire cluster to be "re provisioned" without
have into re-image disks. Reboots are quicker
(for the hardware I use) and since I use ram
disk approach (Warewulf/Perceus) I find that things
are a bit faster, also the diskless image has
minimal services running vs a disk-full distribution image.
(I fully understand the good admin can trim a
disk-full distribution)

There are plenty of arguments either way.  Back in 2006
I did a mini-poll on node disk space usage:

http://www.clustermonkey.net//component/option,com_poll/task,results/id,18/

So "in general, it varies". YMMV

--
Doug



>
> Doug:  Diskless provisioning is usually easier to manage.
>
> Hmm, not sure I buy that one. Pretty much any decent cluster distribution
> should:
> * allow you to add a compute node without much more than plugging it in
>   and telling it to PXE boot (diskless or diskfull)
> * Allow you to push a configuration cluster wide
> * allow you to reinstall/reboot all nodes.
>
> Sure installing 100 diskfull nodes takes more network bandwidth than
> booting
> 100 diskless nodes.  The flip side is booting 100 diskless nodes takes
> more
> bandwidth then 100 disk nodes.  For practical uses of clusters either way
> booting/installation is approximately 0% of the annual network bandwidth.
> Certainly installing 1000 nodes from a single fileserver would take quite
> awhile, but various technologies (bit-torrent and broadcast) remove that
> bottleneck.  I'm kinda curious since diskless nodes don't really install
> how
> do they handle heterogeneous hardware.  Say a dead motherboard comes back
> with
> a new pci-id or 3?
>
> Doug:  In general diskless is faster.
>
> At what?  Diskless booting is faster than diskfull booting or diskfull
> installation.  Application performance should be pretty much the same.
> The
> worst case scenarios like installing 1000 compute nodes from the head node
> are
> usually dealt with by using broadcasts or bit-torrent.
>
> So it depends, my current thinking is that it's not worth the man hours to
> do
> it yourself unless you have a larger cluster.  If it's supported by your
> cluster distribution it could easily be worth it.  In the whole scheme of
> things I'd worry about diskless last.  Decide on your cluster distribution
> based on your application and user needs, systems administrator
> experience,
> and budget.
>
>
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--
Doug

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