[72962] in North American Network Operators' Group
Re: Quick question.
daemon@ATHENA.MIT.EDU (Alexei Roudnev)
Wed Aug 4 02:05:46 2004
From: "Alexei Roudnev" <alex@relcom.net>
To: "Paul Jakma" <paul@clubi.ie>,
"Michel Py" <michel@arneill-py.sacramento.ca.us>
Cc: "Nanog" <nanog@nanog.org>
Date: Tue, 3 Aug 2004 22:59:11 -0700
Errors-To: owner-nanog-outgoing@merit.edu
>
> Alexei is talking about something else.
>
> > a duallie will keep the system up when a faulty process hogs 100%
> > CPU, because the second one is still available. That also increases
> > availability ratio.
>
> This is a resource problem, not an availibility problem. A spinning
> application is not going to take down the machine on any modern OS[2]
> and anyway can be dealt with with resource limits, SMP or not,
> presuming your OS supports resource limits.
In theory, yes. On pracrtice, 2 CPU improve behavior dramatically. 4 CPU
makes system too complex (as you wrote beloow).
New P-IV with multi threading may be a good selection - behave as 2 CPU
system but is not so complicated as SMP.
>
> The real problem with SMP is kernel complexity. Drivers that are rock
s/is/was/ (5 years ago). Now most kernels are SMP. I agree that SMP kernels
are much more complicated, but we _already_ paid this price.
In reality, applications are less reliable on 2 CPU systems (if they have
some kinds of bugs, which make sense on SMP only),
so I agree with you in some cases.
