Dumping to an exabyte tape drive
Robert Scott
zeke at shamash.cdc.com
Wed Sep 5 05:01:21 AEST 1990
In article <877 at iiasa.UUCP>, wnp at iiasa.AT (wolf paul) writes:
> In article <1990Sep1.143812 at suned1.nswses.navy.mil> jht at suned1.nswses.navy.mil (Jim Tibbs) writes:
>
> Stuff deleted.
>
> These figures seem quite inconsisten. Which is correct?
> Would someone at SUN care to comment, ideally the person who wrote
> their drivers?
>
> A Standard Tape has a density of 6250 bpi and a length of 2300 feet
>
> Jim Tibbs specifies a density of 43000 bpi and a length of 12000 feet
>
> Derick Linegar specifies 4100000 bpi and a length of 5190 feet
>
> Frank Bresz specifies density of 54000 bpi and a length of 6000 feet
>
> --
These numbers are really only used by the DUMP program to determine length of
tape for volume and "time to finish" estimates. The actual device driver
will correctly write to the device regardless of what you specify in DUMP,
but the dump parameters affect how much of the tape you actually use.
We are using a Delta Microsystems driver here on Sun OS 4.01. I quote from
the Delta Microsystems SS-2000T User's Guide (attributed, but not used by
permission):
Using dump with a 2000T drive is essentially the same as using dump
with any other tape device, except that you get a lot more information
on each tape. Because of the difference in bit density between the
2000T and a normal 9-track drive, and because dump uses the 9-track
drive as its reference in calculating the tape length, the tape length
you provide for the 2000T must be the effective tape length (as if
it were a 1600 bpi 9-track tape capable of storing the same number of
megabytes as the 2000T tape).
Formula for computing the tape length parameter:
size = (((512*blocking factor)+1920)/blocking factor) *
((total Kbytes on tape - 2048)/10667)
The blocking factor is how many 512 byte buffers (the standard
buffer size for dump) should be used in 1 tape record (which
by default is 1024 bytes for Delta). So BF is 2,4,6... (default
of 2). Optimum for Delta is BF=124, or 62 Kbytes/block. Total
kbytes per tape is straight from a table as follows (for Sony
P6 tapes, for domestic U.S.):
15 minute tape: 258 Meg
30 minute tape: 516 Meg
60 minute tape: 1032 Meg
etc....
Example for a full dump command to a Sony P6-120 tape using
optimal block size:
dump 0fbs /dev/device_name 124 103400 partition_name
Hope this helps.
Zeke
--
~~~~~~~~~~~ From the Shrine of the "Last Gasp of ETA Systems" ~~~~~~~~~~~~~
Extra zesty disclaimer: MINE! MINE! ALL MINE! <chortle snort froth drool>
Robert K. "Zeke" Scott internet: zeke at eta.cdc.com
Control Data Corp, Supercomputer Support Group
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