Pertec Tape Drive Interface Musings
drb at msu.edu
Wed Jun 10 10:05:28 CDT 2015
> This hypothetical interface + matching software would be intended for
> archiving old tapes and/or making new copies from archived file
> (i.e., to make new boot media for bringup of an old computer). Key
> features would include preservation of block sizes (even if varying
> arbitrarily) and file marks. I'm not sure if there's already a good
> file format for that, and I have a dim memory of previously reading a
> lament about common archival methods failing to preserve blocking.
The E11/SimH .tap formats are dead simple, and relatively complete as
far as capturing the arrangement of the bits on tape. They retain block
size, actual data, file marks, and have a provision for indicating
errors encountered when reading the tape. There was a discussion
recently (simh list?) about standardizing the behavior of the error
marks. The format doesn't have a mechanism for preserving metadata. In
the SimH variant, record lengths must be even. In the E11 variant, they
on't have to be. Otherwise, the two are equivalent.
Using dd to read tapes to disk discards the block size information.
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