More stuff from the Sun rescue

[jvdg at sparcpark.net]

Chuck Guzis wrote:

> On 30 Oct 2007 at 10:19, Sridhar Ayengar wrote:
> 
>> Refresh my memory how those worked?  Two processors in lock-step?  Three 
>> processors in a voting quorum?
> 
> Nothing that simple.  Special software and hardware.  As was driven 
> home to me by a Tandem engineer who was also a good friend, the term 
> of art used by Tandem is "Nonstop" not "Fault tolerant".  A world of 
> difference between them.  For a very good analysis, check out the 
> paper "Why Do Computers Stop and What Can Be Done About It?" by 
> Tandem's Jim Gray.  It should be somewhere on the web, given its 
> importance.  It describes in very eloquent terms, the Tandem 
> philosophy.

I always found Tandem machines a joy to work on. NSK/Guardian/TACL is a nice OS, the user is nicely close to the hardware (unlike IBM mainframes, for instance). Almost UNIX-like.

The hardware's not too shabby, either. We once had a Tandem engineer over because one CPU on our (16-CPU) machine was constantly giving errors. When he finally decided the best course of action was to replace the CPU, he simply yanked it out. The machine kept running like nothing happened. A new CPU was inserted and in the process monitor you could literally see processes moving from their back-up CPU's back to the newly installed one, which was their primary. All of this without any of the programs running skipping a beat.

They had cute promotional items, too. One of my favourites was a coffee mug with two handles on it.

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