🚀 go-pugleaf

In article <186@bally.Bally.COM> pete@bally.Bally.COM (Pete Gregory) wrote:
>In article <17911@ut-emx.UUCP>, jjr@ut-emx.UUCP writes:
>> I use "cat list | backup -i -f$DEVICE -d$DENSITY -C$CLUSTER"
>> to backup files to a streaming tape cartridge.
>> What are the appropriate values for $DEVICE, $DENSITY, and $CLUSTER?
>> I have been using $DEVICE = /dev/rmt8, $DENSITY = 700 bytes per inch
>> (default value), and $CLUSTER = 2000 blocks.

/dev/rmt8 pre-tensions the tape, doesn't it?  You probably don't need this if
you re-use your tapes every few weeks.  I usually use /dev/rmt0.

>Why not use cpio?

If your system gets trashed, you can re-install it from the standalone
diskette if it's a backup archive.  The standalone system doesn't
include cpio.  Read the manual for limitations.

Beyond that, the choice of archive format ia a matter of personal
preference, usually based on the user interface.  IBM people tend
to use backup for everything, BSD partisans use tar, USG users
favor cpio.

>We have had great success using HUGE buffers, huge enough
>that we REALLY stream the drive (it never stops).

Different utilities have different limitations on the maximum buffer
size.  Tar re-sets it to 800 blocks when I ask for more.  The
documentation is unclear, however, as to whether those are 512-byte
blocks or 10Kb blocks, the default blocking factor for tar.

I'll repeat my call for a generic tape-handling program that understands
clusters.  The manuals don't give enough information to enable me
to write one myself.  The worst limitation now is that dd doesn't
understand clusters, so I can't use the drive efficiently to do
a backup over the network with a command like

	tar cfb - 1 directories | rsh remotehost dd obs=20 > /dev/rmt0

What's needed is a program that would fit into the pipeline after dd
and do the block/cluster management, like the `tcio' program that
HP provides for their drives.

	Chuck Karish		karish@mindcraft.com
	(415) 493-9000		karish@forel.stanford.edu