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Re: Server hardware




>
> Hi.
>
> We're about to upgrade our web server, and we finding a hard time
deciding
> between 2 configurations:
> 1. Dual Pentium II 450Mhz
> 2. (single) Pentium III 733Mhz
> Memory will be 256MB and the HD will be IDE 7200RPM.
>
> The server will be used mainly as a web server (for a rather busy web
site)
> but also as a POP/SMTP server with some misc work it has to do (mainly
> cleaning up, firewall stuff, IDS, etc).
>
> Now the question:
>
> Assuming both hardware configuration are the same price (they are),
which
> will have the better performance from your experience? (the actual
question,
> is what is more important for apache: More Mhz, or another CPU?).

Most defintaly the SMP option. Doubly so if you have a very dynamic site
or if you're running some other kind of software that forks multiple
proccess like some security assement tools I know... <wink wink nod nod>
;-)

I'd usually prefer two machines instead of a single high performance one
because of Linux (current!) lack of some usefull high availability
features - but because its so chreap and flexible you can make up for it
by using multiple machines and load balance them inteligently; but of
course, this solution will cost more and is more complicated, although
maybe not as more and as complicated as you'd think...


> I'd also like to hear about your experience with Dual processors on a
Linux
> server (we're talking RH 6.1). Does anybody have any good experience
with
> it? Bad experience? (once again: I'm talking about a web server, not a
> personal workstation) I heard some network cards had problems with Dual
> machines. Anybody heard about it?
> In general - is there any issues I should know about before buying it?

Welp, I have no experience with dual proccessors, but with quad
proccessors:
At least with RH5.2 I have a very positive experience, save for the loopy
clock quirk that was already mentioned by Ira, but which I think the
newer kernel in RH6.1 does not suffer from (but I may be wrong). Anyway,
runnnig xntpd or the likes is a good idea.

You should be aware though that under extremly high loads what will
hamper your upscaleing with an SMP machine is the single kernel lock
linux SMP uses (OK, in the latest kernel version the kernel actually have
a finer granual lock but much of the kernel still doesn't use it):

To quote our Fearless Leader: "A single kernel lock to protect the
integrity of kernel data is the simplest way to do a reasonable SMP, but
it has the problem of not scaling very well on certain types of work-load
(anything that is very system-call intensive, like a web server, for
example). It works beautifully for many things (parallell makes etc), but
it's not a really good answer in the end. "

This shouldn't scare you too much... just be aware of it - as I said,
we're talking very high loads here. But if you're talking about a realy
serious site this is just another good reason to go with the "multiple
cheap machines" solution rather then the "single big machine" (whether is
SMP or not) when thinking about Linux based web servers.

Good luck,

--
Gilad Ben-Yossef
Programmer, Netizen & Geek.
Work: gby@gtek.co.il | http://www.gtekil.com
Play: gilad@benyossef.com | http://benyossef.com
68C7 7C5B 839B 303A FA71  FA4D 0438 0400 3FBE 6986
"WOM:(n) Write Only Memory. Used to implement the /dev/null device found
on Unix machines."



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