Subject: Re: various scsi questions
To: Manuel Bouyer <firstname.lastname@example.org>
From: Peter Seebach <email@example.com>
Date: 02/08/2000 14:54:39
In message <20000208214749.A1238@antioche.eu.org>, Manuel Bouyer writes:
>1) what is really ultra2wide scsi (the one at 80MB/s) ? does it uses the same
> cables as Ultrawide ? Can I mix ultra2wide and Ultrawide on the same bus ?
> (I've never looked at ultra2wide scsi devices yet :)
U2W is most often (always?) found as "LVD", an electrically different kind of
68-pin cable. Not the same cable, not compatible. All the devices I've seen
so far can be jumpered to go back to being plain ultra-wide.
>2) with a dual-channel scsi board, do we have twice the bandwidth (i.e. can
> the controller manage I/O from both channels at the same time) ?
Depends on the exact board, but generally, yes.
>3) which scsi board would you use (supported in -current or in the near future
> of course :) ? I'd prefer 64bits PCI boards, and PCI slots usage may be an
> issue so dual-channel boards may be an option if it's worth it (I think
> I'll need 4 scsi busses in this machine).
I don't know about 64-bit boards. I've generally been happy with Symbios
Logic controllers. I don't know what support is like in NetBSD for the
U2W controllers, but the UW ones work great, and are reasonably priced.
Adaptec's controllers are more expensive (by a lot) and I haven't had
measurably better luck with them - and it's worth noting that NetBSD doesn't
support several of the new ones, or at least, didn't last I checked.
I'm using a pair of EIDE drives on an Alpha as a "low-end" NFS server. With
2 6GB EIDE drives, I can pretty much saturate 100Mbps ethernet with packets,
and I get at *least* 5MB/sec.
Keep in mind, your network will limit you long before disks will. My advice
is generally to not spend too much extra money on extra speed in disks, unless
you have some way to get the bandwidth used.