I think I have the answer, from two memebers of the List who emailed me
>I've had seven disks in the same machine. The power supply didn't
>like it, though. I currently have five disks, a CD-RW/DVD and no
> >Assuming one has all space in available bays, that's the question.
> >The PC is running Debian linux, woody, and is a Gateway Intel Pentium III,
> >I think. It's a tower, with plenty of free bays for an hd of any size.
> >Again, I don't read the newsgroup often -- so direct email would be
> >greatly appreciated.
> >I'll summarize when the answer is known, to the net.
> If you put a hard drive on the same channel as a slower device like
> a CD, it'll take a serious performance hit any time the slower device is
> in operation. IDE can only perform one operation at a time.
> A plug card with two IDE channels can be had for less than $25.
Since my application is for occasional backup, a performance hit is no
issue -- and my CD is only rarely used.
So, it seems I can safely install a big IDE disk in the machine -- at
worst, sharing the same device as the CD player.
Actually, I may simply transfer one of the hd's in the machine -- one
that is used very little, and is a small hd -- to another machine that's
always running, and that currently has only one (big) SCSI disk -- it's
used as the fileserver for the network.
(I wouldn't want to put the new backup disk on the fileserver -- the idea
is, to back up -- mostly -- the fileserver, in case of a catastrophic
failure of, either the whole fileserver machine, or at least the (crucial)
SCSI disk, containing most data).
Thanks much, M?ns and Adam, for your timely and useful responses!