[Simh] VAX Tape Emulation?

[Clem Cole]

On Wed, Jan 24, 2018 at 5:25 PM, Zane Healy <healyzh at avanthar.com> wrote:

>
>   I’d like to backup to a simulated tape drive on the one emulated VAX.
> The largest drive on my Alpha is 50GB.  I’d prefer not to have to span
> tapes. :-)

​Another thought...  what are you running the emulator on?  Is it a
UNIX/Linux flavor of some type?   I ask because there might be another
solution that could work a little better in practice, although you'll need
to pull together some pieces.      The problem is the bits in my brain WRT
to VMS are 20+ years old and I've forgotten the details so you'll have to
do some homework.

At one point, I remember that some VMS folks in ZK3 (CJ Coppersmith seems
to stick in my head by I do not remember) were messing we putting a the UCB
sockets library into VMS and were somebody ported the Berkeley rcmd(3)
suite on VMS from Tru64.   I'm not sure if how much of that library or
which commands ever saw the light of day in a production version of VMS.
But the idea (then) was that a VMS system could use remote services (such
as a tape) via a socket.  The UNIX command is called rmt(8) (and of course
mt(8) and IIRC rmt(8) was originally based on the rcmd(3) calls from
rsh/rcp et al.

So assuming VMS supports same, using mt(8)/rmt(8) is trival on a UNIX side.
    But more importantly for you is that on the UNIX side the remote
'device' can be a UNIX file as easily as a physical tape if the 'source'
side knows about using a socket as the output 'device.'.  I've used this
trick to back up some older systems to modern devices these days (my
Masscomp box for instance).  The "tape files" are stored on my NAS which
has redundant physical disks etc...  In fact,  I've even recompiled mt/rmt
for my Mac at one point and I have it working on *BSD with modern tapes
(just needed to grab the mtio.h file from BSD).
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