8mm tape length for dump

[Chris Torek]

In article <412 at h.cs.wvu.wvnet.edu> fuhrman at b.coe.wvu.wvnet.edu
(Cris Fuhrman) writes:
>Can anyone tell me what the length for an 8mm tape drive is
>while using dump in SUN OS 3.5?

No.

(That is, no one can tell you.)

The length you give to dump is plugged into a formula designed for
9-track tape reels at 800, 1600, and 6250 BPI, and not for any of the
cartridge formats.

Moreover, all existing 8 millimeter tapes (which all use Sony
transports, Sony cartridges, and Exabyte's data format, with the drive
electronics being from Exabyte, so as it happens it does not matter
which manufacturer's 8mm tape drive and cartridge is being used; but
this is an unusual and probably temporary situation) are capable of
writing either `long tape marks' or `short tape marks', and the amount
of data that will fit onto a single cartridge depends to a great extent
on how many long tape marks are written.  This in turn depends on
whether your software and hardware uses long or short tape marks, and
on how many files you put on a cartridge.

In general, however, the average installation has less disk data
to back up than fits on a single one of these cartridges, so any
length close to infinity suffices.  We have been using the command

	dump 0ufds /dev/tape/1n 6250 32000 <filesystem>

but the 32000 here is just a WAG, and depends on this `infinite
length' property.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris at mimsy.umd.edu	Path:	uunet!mimsy!chris