Re: How can I share a HD with two //GSes?

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <3t281b$bvk@hearst.cac.psu.edu>,
Jason Jeffries <JJeffries@psu.edu> wrote:
> I may be getting another GS. I've got a RamFAST card with a 130 meg
> drive in the GS I have now, and would like to be able to share it with
> the other GS.
> 
> I know I could do something of the sort with a Mac acting as a sever,
> but I don't want this--I couldn't boot from it without Apple's
> expensive server software anyway.

You wouldn't want to, either.  Data is transferred over LocalTalk at a
similar speed to a floppy drive.  Booting over the network is a rather
slow operation, especially if the network is being used for anything
else.

> I want "real" networking--just the GSes.

Sorry, not available unless someone wrote some LocalTalk file sharing
software for the IIgs.  This would be a major amount of work.  The end
product would not be as good as using a Mac as a server, and you would
still have the speed restrictions of LocalTalk. 

> If it's possible, how do I do it? If I would get another SCSI card for
> the 2nd GS, would they coexist in peace, or corrupt the HD?

Nope.  The RamFast cannot coexist with another SCSI master - it
doesn't support "SCSI arbitration", which means that if two computers
try to access the bus at once, the RamFast will try to communicate
with the peripheral no matter what the other one does.  This may
result in data corruption during any read or write operation.

The Apple SCSI card (High-speed, at least) does support SCSI
arbitration, so it can theoretically coexist with another SCSI bus
master that also supports arbitration.  In practice, this is of rather
limited use, because the operating system cannot prevent conflicting
accesses to the hard drive.

In particular, if either computer can write to the drive, the other
one is in danger of reading garbage.  If both can write to the drive,
there is a high likelihood of data corruption.

It is really only safe when both computers have access restricted to a
shared read-only device (e.g. a CD-ROM, or a write-protected partition).

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand