Re: Hot pluggable CPUs ( was Linux 2.5 / 2.6 TODO (preliminary) )

[Bruce Guenter]

On Sat, Jun 03, 2000 at 08:44:37PM +0100, James Sutherland wrote:
> > So, you've essentially got two complete systems (once you add up all the
> > components) in a single box. 
> 
> No. I have the same components, but organised to make one single machine
> with N+N redundancy, rather than a pair of independent machines with no
> redundancy at all.
> 
> > What does this buy you above having two completely independant boxes?  
> 
> Redundancy. Your approach gives you two machines, each with, say, 99.99%
> availability. Mine gives a single machine with, perhaps, 99.9999%. Two
> machines without redundancy have much lower availability.

I was referring to N machines with network-level redundancy instead of a
lower-level redundancy (either shared memory or shared bus interconnect).

> > I wouldn't be surprised if a single box with all the redundant
> > components costs more than the total price of two seperate boxes.
> Yes - you are paying through the nose for the extra 9s of availability.
> There are markets where the client is more than happy to do so; in mission
> critical apps, double the price for an extra 9 is a bargain.

Only double the price?  That would indeed be a bargain.
-- 
Bruce Guenter <[e-mail]>                       http://em.ca/~bruceg/