Re: [9fans] Xen for Windows(Was:vmware 5.0)

[Ronald G Minnich <rminnich@lanl.gov>]

Brantley Coile wrote:

> i was asking Friday here at work, what are the modivations behind VM?

I forgot the other one. Drivers, drivers, drivers. I can run Plan 9 on 
machines that I don't have time/brains to write drivers for. This is 
particularly interesting with a 1024-node cluster here called Pink; I 
can run Plan under Linux on 1024 nodes and do some kind of scaling 
tests. I can also run 10,240 instances of Plan9 on that machine (VM, 
right?) and at least see what kinds of things break when you have a 
10240 node Plan 9 cluster. Of course, it's not going to run at speed, 
but you can still learn a thing or two.

The only interconnect on Pink is Myrinet. Maybe I should write Myrinet 
drivers for Plan 9, but even if I did ...

There's infiniband. I don't want to write IB drivers for Plan 9, at 
least not at present. They're very complex and unsettled.

So, the basic idea is that VM lets you run OSes on machines that 
otherwise it would be very hard to get to, and use many more processors 
than you have in reality.

Also, booting Plan 9 in a second is nice when you're in developer mode. 
Skipping 9load is a good thing, all the way around. Kernel crashes are 
painless.

True story: I went to IBM Palo Alto in 1990 to talk about various 
supercomputing things and the issue of AIX/370 came up. AIX had always 
run under VM to that point. There was really some question about whether 
any living person knew enough about the IBM I/O channels to make AIX 
native. VM knew the tricks; did any human know the tricks? Nobody knew. 
IBM had kind of screwed themselves on this score, as VM went 
closed-source in 1982, and the entire external VM community no longer 
knew enough to help.

[[Another argument for open source: your company might forget how your 
own software works, but the larger community might remember. This type 
of forgetfulness happens way more often than you might think. ]]

To this day, at least Linux is not native, or so I understand; Linux on 
the zSeries always runs under VM. Again, feature: IBM has shown cases 
where 7,000 or more instances of Linux can be running on a zSeries 
machine small enough to fit in your kitchen -- air-cooled at that. No 
need to buy rackfuls of machines in that case!

ron