🚀 go-pugleaf

In article <17dknqINN62s@grapevine.EBay.Sun.COM> smckinty@sunicnc.France.Sun.COM (Steve McKinty - Sun ICNC) writes:
>In article <1992Aug25.125103.3101@cs.ruu.nl>, clldomps@cs.ruu.nl (Louis van Dompselaar) writes:
>	> A simple question:
>
>With unfortunately a simple answer: Don't do it!

Or the long answer - it depends on the systems, and your determination...
I've been using a couple Atari ST's and multiple hard drives this way for
a while now.
>	> 
>	> I will have two SCSI devices available in a month or
>	> two and like them both to access two 20 meg SCSI
>	> drives. N.B. of course they both use the same O.S. :-)
>	> Anyway, if networking SCSI is as simple as I hope
>	> it is, could anyone tell me how to do it by E-mail.
>	> if it isn't, does anyone have a good reference where
>	> I can find how to do it.
>
>I assume these are two computers and you want them to share the data
>on the drives? There are two problems with that:
>
>1) Most SCSI hosts are set to ID 7, and some cannot be changed. Since all
>   items in a SCSI bus must have different ID's you _must_ be able to
>   change the ID of one of your hosts. If you can't, you can go no
>   further.

Worse - the ST's host adapters don't have IDs at all. SCSI bus interrupts
tend to arrive on both STs at once.
>
>2) The nasty one: Pretty well all computers use some form of disk caching,
>   that is they store some of the frequently used data from the disk (like
>   bitmaps, directories etc.) in local memory. When you change something
>   e.g. by opening a file, the cache is updated but usually not written
>   back to the disk immediately, perhaps not until 30 seconds after
>   the file is closed.
>
>   If you have two computers, both caching data, it won't take long (a
>   matter of a few seconds) before each machine has a very different idea
>   of what parts of the disk are used. If you write to the disk in
>   those circumstances it will very rapidly become corrupted.
>
>You might get away with mounting a shared disk read-only on one machine,
>but other that that its a very risky thing to do (unless you have an
>OS which supports that sort of thing, like VMS).
>
>Its a pity, I have several machines I'd like to network that way, but
>for now it looks like Ethernet :-(
>
I've been using the ST MIDI ports to send control info between the STs.
Works OK, while the bulk data transfers go via SCSI.
-- 
  -- Howard Chu @ Jet Propulsion Laboratory, Pasadena, CA
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 ::To the owner of the blue Mazda, license 742-XLT, your headlights are on...::
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