[Simh] VAX Tape Emulation?

[Zane Healy]

> On Jan 25, 2018, at 6:57 AM, Clem Cole <clemc at ccc.com> wrote:
> 
> 
> 
> On Wed, Jan 24, 2018 at 5:25 PM, Zane Healy <healyzh at avanthar.com <mailto: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).  

Interesting…  I wonder if this is an option in the latest versions of OpenVMS.  I was already researching OpenSource VTL options.  The problem being a distinct lack of support for OpenVMS in any OpenSource backup software that I could find.

Zane



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