[Beowulf] best archetecture / tradeoffs

Tim Mattox tmattox at gmail.com
Sat Aug 27 18:32:46 EDT 2005


Hello Seth,
Two minor additions/corrections about Warewulf that I'll add to RGB's
wonderful (as always) reply...

In Warewulf, the VNFS is short for Virtual Node File System, and it is
a complete* filesystem that is the template for the nodes in your cluster.
This VNFS resides on the master/boot server, and is used to construct
the root filesystem for each node in your cluster.  You can make changes
to this template directly using chroot, or indirectly with other scripts/tools
for example:  rpm --root /vnfs/default ..., or yum
--installroot=/vnfs/default ...

Also, in early versions of Warewulf (circa 2003), the entire root filesystem
for a node would need to reside in RAM in it's ramdisk.  However, in more
recent versions, we introduced a hybrid NFS/ramdisk scheme that reduces
the permanent RAM footprint dramatically by using a readonly NFS mount
of the VNFS for non-critical files. Thus, you can have your full blown text
editor, compiler, and X installed in the VNFS, yet still have only a 15 to
30 MB ramdisk on the nodes.  Which files reside on the ramdisk vs. which
come from the NFS mount are configurable when the ramdisk image is
created.  Thus, you can get much of the small-RAM-footprint benefit of
the NFS-root scheme, yet have dramatically lower NFS traffic to the server
during normal cluster use.

*the VNFS does not contain the kernel, nor the /boot directory, among a
few other minor missing parts that are supplied at network boot time.
-- 
Tim Mattox - tmattox at gmail.com
  http://homepage.mac.com/tmattox/
    I'm a bright... http://www.the-brights.net/

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