[Beowulf] open mosix alternative

[Tony Travis]

Geoff Galitz wrote:
> [...]
> I think the idea is that MOSIX functionality is more easily developed 
> and deployed in the form of virtual machines than directly at the kernel 
> level.  There are some trade-offs, of course... more overhead being 
> chief among them but the virtualization model is clearly the overall 
> favorite.  It sure does beat the heck out of having to track each kernel 
> individually.

Hello, Geoff.

MOSIX functionality is mainly about load-balancing between independent 
kernels, and avoiding severe memory depletion by migrating processes 
between kernels. In fact (open)MOSIX implements an SMP-like model, but 
with a high-latency interconect (usually GBit ethernet). There is no 
need to 'track' kernels, because the oM HPC extension does it for you.

The principle objective of SSI computing is to use many small machines 
as if they are one big one. This is the opposite of virtualisation which 
uses one (or a few) BIG machines like a lot of small ones. It does this 
by virtually separating the kernels. There is some confusion about this 
because it *is* very convenient to teach about or develop and test SSI 
software on virtual compute nodes if you don't have a lot of real nodes, 
but it defeats the purpose of SSI to use this approach in production.

You might be interested to know that one reason Moshe Bar gave when he 
announced the end of the openMosix project was that SMP is now so cheap 
that SSI clustering less of a factor in computing:

	http://sourceforge.net/forum/forum.php?forum_id=715406

I'm not sure I agree - I still find openMosix useful, and I'll continue 
using it on our Beowulf here until I find a better alternative.

	Tony.
-- 
Dr. A.J.Travis,                     |  mailto:ajt at rri.sari.ac.uk
Rowett Research Institute,          |    http://www.rri.sari.ac.uk/~ajt
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