[Info-vax] strange backup behavior

[AEF]

On Aug 10, 6:40 pm, glen herrmannsfeldt <g... at ugcs.caltech.edu> wrote:
> AEF <spamsink2... at yahoo.com> wrote:
>
> (big snip)
>
> > I'm experimenting with appending backup save sets on an 8mm drive. I
> > have DLT, but no scratch tapes to play with. I'll report back when I'm
> > done.
>
> With DLT and LTO using serpentine recording, it is possible
> to seek to EOD or rewind without running the tape for the full
> recorded distance.  That assumes the proper communication between
> the program, driver, and hardware.
>
> Helical scanned DDS and 8mm don't have that ability, though they
> may still have a fast seek mode.  (That can sense tape marks even
> without reading the bits.)
>
> -- glen

I have a TZ88 and it seems to take a long time to get to the end of a
long save set. Have you checked? Why would the drive have 128 heads?
Sounds pretty expensive when one would do! (Actually, it has two. See
below from the TZ88 manual.

1.4 Reading and Writing Data
The TZ88 Model 20/40 GB DLT Cartridge Tape Drive writes 64 pairs of
tracks — 128
tracks total — on the CompacTape IV tape. The drive reads and writes
data in a two-track
parallel, serpentine fashion, traveling the entire length of tape on
two tracks. The drive then
steps the head, reverses tape direction, and continues to read/write
on the next two tracks, repeating
this same process for a total of 64 times per tape.

AEF