From: olson@anchor.esd.sgi.com (Dave Olson)
Newsgroups: comp.sys.sgi
Subject: Re: 128Mb MO drives & hard disks
Date: 14 Oct 92 05:49:52 GMT
Organization: Silicon Graphics, Inc.  Mountain View, CA

In <1992Oct12.115727.28658@u.washington.edu> pdanset@hardy.u.washington.edu (Paul Danset) writes:
| Sorry if these are FAQs, but does anyone have recommendations for
| magneto-optical (MO) drives?  I am particularly interested in the
| 128Mb MO drives because of their price (approx. $1100-$1800).
| Would the standard dks SCSI disk driver work with these MO drives?
| Whose drive mechanisms work well with the Indigo (e.g. Sony, Ricoh,
| MOST, Pinnacle, etc.)?  Any recommendations on vendors?

Maybe.  I was waiting for someone who had used one to post, but since
nobody has, I'll try to answer.

Yes, there is a reasonably chance that they can be used with the
normal scsi disk driver (dksc), unless they have some strange
problems.  It is possible if they won't work with dksc to use
ds (devscsi, the generic scsi driver), but my guess is that anything
that fails with dksc will fail with ds, except for a few cases.
About all I can suggest is to buy it with a money back guarantee,
and try it (make good backups first!).

SGI hasn't been too interested in them so far, because of the
limited capacity.  We may look at the newer 3.5" M-O's with 256MB
capacity, but there are no commitments to do so.

| Would commodity MO drives from PC/Mac mail-order houses work, or will
| they have problems due to the difference in block sizes?  Do I have to
| stick to vendors who specialize in SGI peripherals?

If you expect to use the SGI EFS filesystem, you *must* use 512 byte
media, not 1024.  Someday we may fix this, but don't hold your breath.

| Finally, how about commodity hard drives such as the Seagate ST1480N
| (426Mb), Seagate ST41200N (1.2Gb), and the Fujitsu M2624SA (520Mb)?
| I believe SGI ships the Seagates mentioned above, but I was wondering
| if they are shipped with different firmware.

Fujitsu's seem to have firmware that is somewhat less than stable,
requiring exactly correct jumper setup, which for some drives, at
least, includes disabling sync scsi, which will hurt throughput; other
than that, sounds like folks are fairly happy with them.  Yes, we ship
the 1480 and 41200N.  We had them fix some bugs/performance issues, but
I suspect currently shipping drives from seagate have had these folded
in to their firmware; I won't promise that they will work the same/as
well, though.

| My system is an older R3000 Indigo running 4.0.5.A; it appears to
| come with the SCSI bus (as opposed to SCSI-II for the newer R3000
| and R4000 Indigos ... please correct me if I'm wrong).

Depends on how you define SCSI-2.  All SGI systems support a very
large subset of SCSI-2.  The r4k indigo and the most recent r3k
indigo's have the WD 93B rather than the 93A, which means that they
will *negotiate* fast SCSI (which some folks refer to as SCSI-2),
but the DMA engine was designed for the 93A, so the change only
helps about 10% for drives that do in fact support fast SCSI (that
is, we can sustain 5.5 MB/s instead of about 4.9 MB/s during the
data phase portion of a command; actual sustained rates will of
course be somewhat lower due to command and other bus phase overheads).

The only drive SGI is currently shipping that supports fast SCSI
is the IBM 1.2 GB drive, which is actually a somewhat slower drive
(disk rate) than the 1480, at least, for part of the drive.  The
1480 is a zoned drive, and the IBM is not.  All in all, the 93B
can help a bit (with multiple drives on the bus!), but not
dramatically.

Future SGI systems will actually run at very close to 10 MB/sec for 8
bit fast scsi (newer dma engines); we will also have fast and wide at
some point (but I couldn't say just when).
--
Let no one tell me that silence gives consent,  |   Dave Olson
because whoever is silent dissents.             |   Silicon Graphics, Inc.
    Maria Isabel Barreno                        |   olson@sgi.com