Quick question.

Thu Aug 5 05:53:30 UTC 2004

On Wed, 4 Aug 2004, Alexei Roudnev wrote:

> I am sorry, but I do not make a theory - I just repors practical 
> results. 2 CPU systems are much more stable than 1 CPU system, in 
> my experience. You are free to find an explanatiion, if you want 
> -:).

The theory suggests your experience is unusual, or that you're 
overemphasising one positive contributor towards system reliability 
of complexity against the negative impacts of complexity.

Again, I'm not arguing that the more complex system (eg SMP) must 
always be more unreliable, a well-engineered complex system will be 
more reliable than a simple but badly-engineered system. I know of an 
SMP PC server that hit at least 4 years uptime (never rebooted while 
i was in the employ of that company anyway ;) ), however it would 
have been just as reliable with just one CPU. And for a large sample 
of those machines, identical other than single and dual CPU, the set 
of single CPU machines will be statistically more reliable. Further, 
for a diverse sample of hardware of varying quality, you will see far 
more problems with SMP systems - primarily due to software (eg 
drivers with subtle locking bugs).

Nor am I arguing that the tradeoff of reliability for better 
performance is unwise, particularly since in this case (SMP systems), 
CPU failures tend to be rare (unless secondary due to some other 
failure, eg cooling).

anyway, I'm repeating myself, so i'll stop before susan larts me, and 
let the list get back to its favoured topic of discussing analogies. 
;)

regards,
-- 
Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
Fortune:
You're working under a slight handicap.  You happen to be human.