Why no rlogin to nodes?

[Daniel Ridge]

Colleagues,

Robert got this just right (except the spontaneously ionizing bit :),
and what follows are some amplifications that (I hope) will relate
to the situations of some potential users who may read this list.
 
On Mon, 16 Oct 2000, Robert G. Brown wrote:

> One very nice thing about it that I plan to try is that you don't have
> to totally commit to it to give it a spin.  I think, from what Erik and
> Don said at different times, that it works best if you can give the
> distribution a GB or two of hard disk on the "master node", but the
> nodes can boot non-destructively from their CD's or floppies (leaving
> their current install images intact).  Since the nodes pretty much run
> out of ramdisk after boot, they don't need room on any local disk.

A number of people have asked us about the 'footprint' of
Scyld Beowulf. Our distribution expects to find two things on
every node: a tiny ramdisk root filesystem and a collection
of cached libraries. We currently cache about 35 megabytes of
libraries on the clients and the tiny root filesystem is on the
order of a megabyte. The library cache may be installed in either
a ramdisk or on a hard disk. 

The library cache is what allows us to keep bproc_move calls fast.
BProc won't waste time or bandwidth transferring mmaped() copies
of libraries along with a process unless that (version of) that library is
not cached on the nodes.

> So you don't have to do much of anything to try it out, provided that
> you've got a tiny bit of free space on a "master" node somewhere.  If
> you don't like it, just put lilo back the way it was and delete it.

You can even do one better. Right now, I'm running a copy of VMware on
my laptop -- this VMware instance is connected up to my laptop (which
is running Scyld Beowulf) as a slave node! Obviously, this setup is
tailored more for debugging than for high performance. 

In a similar way, you can run a Scyld Beowulf frontend load inside
VMware.

Regards (and Good Luck!),
	Dan Ridge
	Scyld Computing Corporation