Re: Drunken mumblings [OFFTROPIC]
Dancer (dancer@zeor.simegen.com)
Fri, 01 Jan 1999 10:29:10 +1100
"Richard B. Johnson" wrote:
>
> On Wed, 30 Dec 1998, John R. Lenton wrote:
> [SNIPPED]
> >
> > Can a SCSI cable be used to connect computers? I mean, can a
> > computer be daisychained with say a hard disk? In theory at
> > least? Using a special card?
>
> A SCSI disk (or any SCSI device) can be "shared" by other masters on
> the SCSI bus. The master only has to win arbitration (it's done by the
> chip), and it can access any device that wants to be accessed. I use
> "want" here in a particular way. A SCSI Host controller, and its driver
> software, generally doesn't "want" some other SCSI master telling it what
> to do.
>
> Therefore, communications with a device such as a disk, by two separate
> computers, is not a problem. You can, in fact, use a common hard disk
> even to boot two different machines. The problems come if one or more of
> the machines tries to write to the disk.
This sort of setup (two machines sharing one or more drives via a SCSI
chain) was not outrageously uncommon, back in the mid-80's. You've got
to be willing to have zero read/write buffering, and have your
filesystem make a few concessions. IE: Performance degrades.
D
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