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Subject: Re: [OMPI users] cluster LiveCD
From: Abhishek K (abbyzcool_at_[hidden])
Date: 2008-08-08 09:18:07


On Fri, Aug 8, 2008 at 3:53 AM, Adam C Powell IV <hazelsct_at_[hidden]>wrote:

> [Off-list because it's off-topic]
>
> Thanks for the link. But from the website I can't quite tell what
> exactly Perceus is, except for "the next generation" of the "de facto
> standard". Do you have a link to a good explanation or architecture
> description?

http://www.perceus.org/docs/perceus-userguide-1.4.0.pdf
HTH, this has a nice high-level view of how Perceus works.

>
> And in terms of de facto standards, isn't LTSP pretty much ubiquitous?
> What more could Perceus be, than some kind of PXE booting, with some
> kind of network file system?
>
> Thanks again, I'm all ears...
>
> -Adam

One of the most obvious differences that comes to mind is: LTSP uses a
NFS-root only approach which is why it isn't particularly favored in HPC
environments. Mounting the entire root filesystem over NFS always leads to
increased network activity since the filesystems seems local to most
applications. The usual way around this is to create symlinks that point to
the local disk or RAM (See http://www.onesis.org)
OTOH, Perceus uses a hybrid approach, in that it loads a minimal local OS in
the RAM and mounts a networked filesystem; which reduces the network
bandwidth and latency.

If this is being way too off-topic, the Perceus/Warewulf mailing list (
http://lists.caosity.org/mailman/listinfo/warewulf) might be a good place
for this discussion.

 -- Abhishek

>
>
> On Thu, 2008-08-07 at 15:03 -0400, Tim Mattox wrote:
> > I think a better approach than using NFS-root or LiveCDs is to use
> Perceus in
> > this situation, since it has been developed over many years to handle
> this
> > sort of thing (diskless/stateless beowulf clusters):
> > http://www.perceus.org/
> > It leverages PXE booting so all you need to do on a per-node basis is
> enable
> > PXE booting in the BIOS. The primary limitation I see would be if your
> > windows machines are set up to use DHCP to get their IP addresses from
> > some server that is outside your control, since Perceus would need to
> take
> > over DHCP services to do its magic.
> >
> > On Wed, Aug 6, 2008 at 6:05 PM, Adam C Powell IV <hazelsct_at_[hidden]>
> wrote:
> > > On Tue, 2008-08-05 at 17:01 -0500, Ben Payne wrote:
> > >> Hello. I am not sure if this is the correct list to ask this
> > >> question, so if you know of a more appropriate one please let me know.
> > >>
> > >> I think am looking for a LiveCD that supports MPI, specifically one
> > >> that has mpif90 built in, and can easily mount external (USB) drives
> > >> for storing data.
> > >>
> > >> I have access to 40 Windows computers in a lab that rarely gets used.
> > >> I would like to use the computers to run a cluster during the
> > >> weekends, but be able to not mess with the Windows installation that
> > >> exists on the hard drive. Because of this, I think a LiveCD would be
> > >> good, and one that supports PXE booting is even better. If there is a
> > >> better way to do this (run MPI, not disrupt Windows) please let me
> > >> know.
> > >
> > > The easiest way to do what you want is probably to netboot from a
> server
> > > on the subnet with NFS-root. That way you don't need to make a bunch
> of
> > > new CDs to upgrade a single piece of software. Just upgrade/modify the
> > > environment on the server, and everybody else upgrades instantly.
> > >
> > > Turn on the server and reboot the machines, and you're in Linux with
> > > MPI. Disable PXE at the server and reboot and you're back in Windows.
> > >
> > > LTSP has some tools to do this, as does the Debian package lessdisks.
> > > The basic principle is in http://wiki.debian.org/DebianLive and
> > > http://wiki.debian.org/DebianEdu/HowTo/LtspDisklessWorkstation . The
> > > old diskless package did this beautifully, but bitrotted and is
> > > deprecated due to lack of maintenance.
> > >
> > > -Adam
> --
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