ADVENT #7 — lto tape

I originally thought the Alice write-once tape would be useful for secure electronic voting machines. It turns out that people either believe elections work or they don’t — no matter what the technology. Maybe black boxes for airplanes that could record the computations governing flight, not just the telemetry. Instead, I mostly use it to draw.

Once I have a program tape that captures a drawing, it’s pretty easy to replay the tape to re-render the drawing as SVG for browser or plotter, as gcode for CNC machine or 3D printer, or as input to a computerized embroidery system. This last one remains aspirational — so adjust your expectations for Paper Tiger merch accordingly.

In Alice LOGO, you can do all the usual logo things. Left turn, right turn, pen up, pen down, pen color, forward, and back. You know, if you could ask the turtle for an inventory you could practically play it as a character in Zork.

Speaking of forward and back, today’s removable media is the LTO digital tape. I was a little hard on the Sinclair zx micro drive in the last installment, so I wanted to give high-end enterprise tape an opportunity to shine. Or shoeshine, anyway. Like micro drive, LTO is a single spool cartridge. Unlike micro drive, it is not a continuous spool. Instead, the drive contains an empty take-up spool. Like an 8-track, the tape makes several passes through the drive as the heads access each track area. Unlike the 8-track, the tape reverses direction at the end of each pass. More like lap swimmer than circumnavigator. You could probably program a tape drive with logo.

The densest LTO cartridges today hold 18TB and cost around a hundred bucks each. An 18TB hard drive goes for only double that. Of course, the LTO tape drive costs about four thousand dollars, so you break even on a per-byte basis at 40 tapes. You just need a robot to … oh. A robot that holds 40 tapes is around fifteen thousand dollars. Well, there is probably some way that this makes sense. Archival, perhaps. Tapes guaranteed to outlast the last drive capable of reading them.

I do have a soft spot for these drives, though. They offer an optional WORM format that could host a write-once Alice tape natively. One other thing I like about LTO tape is that it can run at variable speed so that it doesn’t overrun a reader’s buffer and have to stop. That’s the inspiration for the Dartmoor hydrocapstan drive in the unfinished Merrimac stories. Speaking of reader’s buffers, I‘m falling a little behind real time in this series, so apologies in advance for the short pieces to come.