Pertec Tape Drive Interface Musings
cclist at sydex.com
Tue Aug 4 21:20:56 CDT 2015
On 08/04/2015 06:17 PM, jwsmobile wrote:
> I was on the SCSI committee when the tape commands were proposed. The
> original that was proposed was to only have a commands which would be on
> disk controllers (who were the main players) to perform backups of disk
> units and restores. Luckily that effort was headed off by having
> several parties who made tape devices other than Archive join the
I know the feeling from my short time with X3J3 (Fortran (was supposed
to be 88, but became 90)). The reps from DEC and IBM both threw a hissy
fit and threatened to withdraw if the committee didn't ratify their
particular extensions. It was not a nice experience.
It's really odd that the raw Pertec-style interface, even with its
various vendor extensions, is still more robust and versatile than the
SCSI version. On the other hand, the SCSI standard (X3T10?) does a
pretty good job of generalizing tape robots.
> Amazingly I've never had a 4mm or 8mm tape fail to read for media
> reasons. I'm going on having media from both that are as old as the
> technology. My 8mm backups have only one bad tape in the pile, and it
> was marked as written "incomplete" and bad at the time of creation. Half
> inch I've had the same problems documented with the quality of the
> media, but it is much older.
Wasn't Exabyte the only vendor of 8mm tape backup? I've seen other
brands but they all seemed to have Exabyte internals. 4mm DLT is/was
remarkably robust, particularly when you consider the mechanical
intricacies. I was really surprised to see the medium extended to
DAT-320. Apparently, there's yet another generation in the works.
On the other hand, the consumer-level tape backups are really terrible;
Travan, DC-2100, etc. The worst of the bunch was the Datasonix Pereos
that used a (wait for it!) 2mm tiny tape cartridge that one had to order
from Datasonix via Fedex. Thankfully, that one was brief.
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