Pertec Tape Drive Interface Musings

On 8/3/2015 9:54 PM, Eric Smith 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. Eventually a proposal was made for the capability to recover data when blocks on tape exceeded the size of the read request. I had to explain such things as read reverse, and how EOT processing was done on half inch as they all had defined things which made using such devices impossible. The defined command set was still not useful as pointed out by Eric in the area of errors. That tape marks were not records was also a huge debate, and as Chuck points out elsewhere it was not handled consistently either. I still am not happy that the quarter inch products turned out to be garbage and noone called them on it. Even 3m at the time eventually admitted that the physical design was flawed for the speeds that most drives ran the tape at, but never made clear to people how bad the design was. Only when you tried to restore data and it was crap did you become a member of the club that didn't use the QIC devices. 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. thanks Jim