[Info-vax] Backup TK50 tapes

[Stephen Hoffman]

On 2013-02-24 16:02:55 +0000, Dennis Boone said:

>  > While i'm sure there are more modern utilities to copy tapes, providing
>  > you know the block structure of the tape, dd should copy it verbatim,
>  > even if you have to write a script to read it block by block.
> 
> NO NO NO!
> 
> I love dd and all, but it THROWS AWAY BLOCK STRUCTURE and leaves you with
> a byte stream.  The block structure is important on tapes.
> 
> Don't use dd to image tapes!

OP: see <http://simh.trailing-edge.com/docs/simh_magtape.pdf> for some 
details.  Tapes can have variable block sizes, and VMS tape kits use 
that mechanism.

Much of this stuff has been discussed in the simh archives, too.  See 
<http://www.mail-archive.com/simh@trailing-edge.com/msg00130.html>, and 
probably some others.  (That mailing list archive is also available at 
trailing-edge.com, but I don't have the direct link to that thread 
handy.)  There are other threads and other tools discussed over there, 
too.

FWIW, if you're not already familiar with the simh archives, they 
contain a wealth of information on tapes and tape images, and other 
related topics.

I've dusted off an old posting on tape tools 
<http://labs.hoffmanlabs.com/node/810>, with some pointers to tools.

...But hauling around a bootable disk image containing the installation 
files — with just the kit files and not the rest of the tape baggage — 
is usually the easiest way.


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