[TUHS] Ultrix Tape: Block Size?

On Tue, Oct 16, 2018 at 1:49 PM Paul Koning via cctalk <cctalk at classiccmp.org> wrote: Yes. There's DECtape (TU55/TU56), there's DECtape II (TU58), and there's "CompacTape" (TK50/TK70) which developed into DLT III and so on to LTO, etc. The carts for original CompacTape and DLT are the same size. The drives are not of identical reliability. TK50 drives jammed and had a variety of physical problems. Even when they were working, their performance was affected by the systems they were attached to. In particular, they are a streaming technology from an era when low-end systems couldn't feed them fast enough to keep streaming, so in the case of the TK50, capacity was always listed as "up to 95MB per tape" because on writes, if there wasn't data in the buffer, the tape wouldn't just stop but you'd get a gap until there was enough data, so your capacity was lower. For reads, it would have to back up a long ways, spin back up to speed and begin reading where it left off, substantially slowing down read performance. By the time DLT III came out, machines were faster and, AFAIK, the hardware buffering was better so you didn't have the same problems. Having cut a few hundred DLT III tapes 15 years ago, I found the tape drives to be absolutely solid. Over the next 10 years we had an every-other-year upgrade/migration because our capacity needs grew rapidly and the cost per drive stayed about the same. I think they were on LTO2 when I left, in a 200 tape/4 drive jukebox. The short version of this is: TK50s were a PITA then, and they still are. -ethan