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Meditations on Magnetic Media:...(1Sep94)
Exabyte, DAT and Nine-track
(from KPNO, NOAO Newsletter No. 39, 1 September 1994)

With the arrival of a DAT tape drive at the Burrell Schmidt telescope this
summer, each dome at KPNO is now equipped with both an Exabyte and a DAT.

As we celebrate this event, let us take the opportunity to once more lecture
on the subject of magnetic media. If you bring your own Exabyte (8mm) or DAT
(4mm DDS) tapes to use to write your data, bring only computer grade
(certified for Digital Data Storage) tapes. Audio grade tapes are not
acceptable and have caused many observers grief over the past few years.

DAT tapes should be 60m tapes (some of our tape drives can't handle 90m
tapes). Exabyte tapes should be 112m (160m Exabyte tapes are becoming
available, but our drives can't handle them). KPNO orders the following types
of tapes for use at the telescopes: Sony QG112MAa Exabyte tapes and Sony
DG60MAa DAT tapes.

If you want to import data on tape to use during your run, please use
lowest-common-denominator recording techniques. For Exabytes, record in 8200
mode (as opposed to 8500 mode) with no compression. For DAT tapes, record 60m
DDS tapes with no compression (neither DDS-DC nor any other style).

One final word: as you may have deduced from other articles in this
Newsletter, the era of nine-track tapes at KPNO is practically over. Don't be
surprised if nine-track drives start disappearing from the domes in the near
future.

Steve Grandi, Bruce Bohannan

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