Exabyte, interoperating VAX and Sun

[Lars Henrik Mathiesen]

We have an Exabyte drive attached via SCSI to a Sun4/280. This works fine,
and we have been using it for backups for almost a year.

However, we also have a VAX-11/785 with an SA482 disk tower (2.5GB) which
severely depresses the LAN for most of the morning when it is backed up to
the Sun. So we have got an Exabyte on trial, and it works (in a way). It
is attached with a DILOG SU723A controller, which speaks TMSCP to the VAX
(TK50 emulation, currently) and SCSI to the Exabyte.

Our problem is that the Sun can't handle the tapes from the VAX. It
usually works all right for the first file on a tape, but it can't find
the latter ones. We have also experienced some crashes (on both machines)
while experimenting with tapes which had been moved from one machine to
the other.

I suspect that some parameter(s), e.g., file mark size, differs between
the drives. The problem is that I can't find a good way of determining any
of them on either machine, much less control them. We don't have source
code for the SUN driver, and much less for the DILOG controller microcode.
In the Exabyte hardware manual it seems that the file mark size is
determined in each SCSI command packet, and I haven't been able to find
anything in the DILOG manual to let me control that.

We are running SunOs4.0 on the Sun4 and MORE/bsd (May 89 release) on the
VAX.

Any insights or helpful suggestions by mail, please; I'll summarize.

Lars Mathiesen, DIKU, U of Copenhagen, Denmark      [uunet!]mcvax!diku!thorinn
Institute of Datalogy -- we're scientists, not engineers.      thorinn at diku.dk