[Info-vax] strange backup behavior

[B Hobbs]

On Aug 10, 2:17 pm, koeh... at eisner.nospam.encompasserve.org (Bob
Koehler) wrote:
> In article <f3e89c46-2e8d-4c1c-bf0b-11124e349... at k13g2000prh.googlegroups.com>, B Hobbs <bdhobb... at acm.org> writes:
>
> > I'm wondering if the emulator's TK50 tape driver is interacting poorly
> > with BACKUP and the SDLT drive.  Ideally, someone with a real VAX, an
> > HP SDLT, and VMS 7.1 could BACKUP a short file to an empty tape
> > cartridge, BACKUP several tens of gigabytes of data to the tape, then
> > BACKUP the same short file to tape, all with timing info.  If their
> > test shows the time for the third BACKUP to be close to the first
> > BACKUP, then my emulator becomes the prime suspect.
>
>    I'm really starting to suspect the emulation.  I wonder if the
>    emulation writer had UNIX in mind, where the default device rewinds
>    the tape every time you close the file on the tape.

If it is the emulator's tape driver doing this, I would have thought
someone would have reported this annoying behaviour before this.

>
>    OBTW, you're not running the emulation on UNIX, are you?  If so,
>    maybe you can tell the emulator to use the no-rewind interface.

Our emulator runs under Windows.  From my first post:

> System configuration and versions:
>   OpenVMS V7.1
>   VMS thinks it is running on a VAX 4000-105A
>   VAX emulator Charon-VAX/XL (Plus) V 3.1 B 50 (VAX 4000 model 108)
>   Windows Server 2003 SP1, v 5.2
>   HP ProLiant DL385, AMD 64 Opertron
>   HP 160/320 GB SDLT, SCSI connection

Additionally the emulator handles the tape drive itself, the tape
drive has been disabled in Windows.