classiccmp server hardware

From: Tom Jennings <tomj_at_wps.com>
Date: Tue Oct 12 14:31:35 2004

On Tue, 12 Oct 2004, Jules Richardson wrote:

> Where's IDE these days relative to SCSI?

Very, very good. Except for really demanding jobs, which mail
and ftp archive is not, SCSI is a waste of money.

> SCSI controllers
> (RAID or otherwise) were always better than IDE - plus you get the
> higher reliability, more flexible bus options etc.

Times change! Drives are far cheaper; >> reliability may still
exist in SCSI, but it's not been borne out in my experience.

> > If you've got a 100Mbit ether, it's unlikely it will exceed
> > the disk or OS speed.
>
> Not so convinced about that - remember that's bits, not bytes; ethernet
> isn't *that* fast (relative to other things).

(I think you misread this -- without special preparation,
you'll never get > 25 - 50 Mbits/sec through it; that's 5
megabytes/sec peak.

But even this is a false measure; it's not realistic or
practical to size a system by the very tip of peak performance
requirements. More empirical tests are appropriate: how long does
it ACTUALLY take to explode mail? What portion of that is spent
on-disk? (My guess, from actually working with giant mailers, is
90% of the time is spent on the net tied up in TCP-open waits!)

> As for mirroring to a seperate machine (if that's what you were
> intending) then disk performance should easily outstrip network
> bandwidth

Even a fair EIDE system on a modern machine will keep 100megabit
ether 100% soaked 100% of the time if you're just copying
data over a wire. But rarely is that how files are moved,
and certainly not over the open internet!

> (and could probably upset the underlying mail software whilst
> mirroring was taking place) -

I simply don't believe this. This is what OS's *do*. Or maybe
I misread this. Temp files disappear during backups all the
time, it's rarely a problem (occasional "file disappeared!" in
the log).

> I'd go for a seperate ethernet link
> between machines just for mirroring purposes in that case.

Utter waste of time. It could improve stopwatch times to complete
a mirror; but who cares unless the time is significant? This is
what computers *are for*, to do drudgery. If you've got the
ethernet on board, by all means, but otherwise it's a waste
without an actual need.

Unless you have a tightly-specified problem and constraints,
it's best to solve problems when the occur.
Received on Tue Oct 12 2004 - 14:31:35 BST