Looking to read past EOT on DDS/DLT/LTO
sieler at allegro.com
Sat Jan 28 19:48:40 CST 2017
> From: Chuck Guzis <cclist at sydex.com>
> I believe that ANSI refers to them as "partitions", IIRC, defined by a
> special page in the MODE_SELECT command. Each partition has its own EOD.
> Using the MODE_SENSE code page 11h will turn up information as to a tape
> bing multi-partitioned.
As it happens, they (partitions vs. set marks) are different concepts.
A DDS-1, -2, -3, -4 can be either a single unpartitioned tape *or* it can
have precisely/exactly/only two partitions.
(I didn't check newer DDS standards)
Completely separately from any discussion of partitions: a tape basically
consists of entries of type "Data" (user data) and "Separator Marks".
The standards (e.g., ECMA-139 / ECMA-150 / ECMA-170 for DDS-1, ECMA-198 for
DDS-2, ECMA-236 for DDS-3, and ECMA-288 for DDS-4) specify:
"In this ECMA Standard, there are two types of Separator Marks
which are referred to as Separator 1 and Separator 2.
Some other standards, e.g. those which define an interface
between a tape drive and a host computer, use the terms "file mark"
and "set mark" to denote Separator Marks.
It is recommended that Separator 1 be equated to file mark
and Separator 2 be equated to set mark.
("file mark", of course, is also referred to as an EOF (End Of File))
I knew DDS-* drives were insanely complicated, but after reading parts of
the standards, I now realize I was grossly underestimating just how
insanely complicated they are!
SDLT-1 supports "set mark" (and they're called that, not "Separator Mark 2"
:), but not partitions.
DLT-1 and Ultrium-1 support neither "set mark" (nor multiple kinds of
separators) nor partitions.
(ECMA = European Computer Manufacturers Association)
ISO/IEC 17462 = ECMA-288
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