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 committee.
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.
--Chuck
