The Ftape Installation and Usage Guide - File marks
A major change in ftape-3.04d compared with the former ftape-2.x and
the sftape driver from pre-3.04 ftape distributions is the use
of a volume-table segment as specified in the QIC-80/3010/3020 and
QIC-113 development standards (QIC organisations home page). The driver
doesn't use the failed sector log
any more for file mark
emulation but produces a volume table entry for each file written to
tape.
The drawback of this approach is that there is a limit on the maximum number of file marks available per cartridge. Each file marks consumes 128 bytes in the volume table segment, the volume table segment has a size of 29k which yields a maximum number of 232 file marks. The volume table overflow extension as proposed by various qic standards (see QIC organisations home page) is not supported by ftape.
The portions of the tape that are occupied by data written with
ftape-4.05 can be recognised by other programs that conform to those
QIC standards (think for example of the software that was shipped
with your tape drive). One can test this by doing a backup with
ftape-4.05 (using the `/dev/qft*
' devices, see zftape devices)
and then use the software that came with your tape drive (you probably
have to reboot to do this) and try to have a look at the volume table of
the tape. There should be entries containing volume labels like
zftape volume 004
However, you will recognise that the time stamp that will be shown by such a program either makes no sense at all or is really out of date. See Vtblc (info file ftape-tools).
Note: it is still possible to read tapes that were written with the original ftape-2.x driver and the sftape driver from pre-3.04 ftape distributions. ftape-4.05 does accomplish this by emulating a volume table. But write access to the tape is denied until you erase it which damages the data on the tape, of course. See Compatibility with ftape-2.x.
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