SCSI vs ESDI
Daniel A. Graifer
dag at fciva.FRANKLIN.COM
Fri May 25 23:53:01 AEST 1990
In article <1945 at east.East.Sun.COM> gsteckel at diag2.East.Sun.COM (Geoff Steckel - Sun BOS Software) writes:
>[...list of attributes of ESDI & SCSI systems...]
>SCSI
> multiple masters (can share devices)
>[...discussion...]
>One SCSI host adapter on that system talks to [...]
>and could be connected to another CPU for a fake network. [...]
> geoff steckel (gwes at wjh12.harvard.EDU)
> (...!husc6!wjh12!omnivor!gws)
I didn't know SCSI supported multiple masters. I've heard of a Macintosh
product that connected two Mac's via their SCSI ports, but I thought there
were two SCSI buses and a gateway in that system, not one bus.
We have two SCSI bus machines here each with >500MB of disk. We also have
one Excebyte 2.2GB SCSI tape system. We can only do unattended backups
overnight on one machine per night. Is it hard to get a SCSI device like
a tape backup system to talk to two hosts? How is contention handled? If
I have a bus that looks like this:
[SYSA]-[DSKA0]-[DSKA1]-[TAPE]-[DSKB1]-[DSKB0]-[SYSB]
How do I keep SYSA from trying to control the DSKB?s ? (Actually, guess this
wont work for me anyways. Each machine has a QIC tape on it as well. That's
too many SCSI addresses (4/system + Exebyte). Maybe someday we'll get SCSI2!).
If this wont work, does anybody make a box that allows one device to sit on
two SCSI buses, and handles the contention between them? You could just
simulate DEVICE-NOT-READY when the device was in-use by the other system.
Thanks in advance?
Dan
--
Daniel A. Graifer Franklin Mortgage Capital Corporation
uunet!dag at fmccva.franklin.com 7900 Westpark Drive, Suite A130
(703)448-3300 McLean, VA 22102
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