[geeks] Re: kernel scalability....

[Greg A. Woods]

[[ moving to geeks.... ]]

[ On Wednesday, September 5, 2001 at 21:16:40 (+0100), Mike Meredith wrote: ]
> Subject: Re: [rescue] This Just In: HP to buy Compaq
>
> I'm not trying to say that the linux kernel is scalable up to zSystem 
> size, but I believe one of the reasons for running thousands of linux 
> partitions under VM is to replace thousands of rack mounted linux boxes 
> in a hosting environment.

Yes, that's "one" of the reasons....

> Using it as "proof" that linux doesn't scale 
> is slightly bogus.

Well, it won't -- take the reasons as you will, but you'll likely never
see any decent sized 390 or similar architecture machine running a linux
kernel on the bare hardware and handling anywhere near the load that you
can push through the same machine with multiple VM partitions.

The real reason why people run thousands of linux partitions under VM is
because they can and because doing so is much less expensive than any
other option.  The physical and operational requirements necessary to
handle the same load with linux kernels running on bare metal of any
kind would be much larger and thus much more expensive.  I.e. that does
definitely mean that the linux kernel cannot, alone, scale into the
upper stratosphere of large computer systems.

Personally of course if I were to get into a situation where I would be
buying or leasing such a solution from IBM I'd find it easy to also pay
them the additional price necessary to port NetBSD to run under VM.
(though that may already be done before I ever have such a need!  ;-)

Of course *BSD won't scale all that well either, at least not without a
lot of tweaking and hacking.  :-)

The likes of IBM and Amdahl have spent many tens of man-years making
Unix scale even half as well as VM on machines with that kind of
architecture, and yet still they recommend running it under VM.

A more interesting comparison of linux scalability would be to compare
it to NetBSD, which runs VERY WELL on everything from the smallest of
ARM or sh3 systems up to the largest DEC Alpha servers, not to mention
on a lot of older hardware.

-- 
							Greg A. Woods

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