Subject: Re: System backups
To: Robert Nestor <>
From: Christopher R. Bowman <>
List: current-users
Date: 01/19/1998 23:46:30
On Mon, 19 Jan 1998, Robert Nestor wrote:

>I recently added a a new Conner/Seagate SCSI tape drive to my NetBSD 
>system.  It is a Travan type drive that can store up to 8gb on a single 
>tape cartridge.  However when I tried to use "dump" to backup my /usr 
>filesystem that currently occupies less than 2gb, I was shocked to see it 
>would take approximately 86 tapes!  Thinking this was bogus and it would 
>run until it found an EOT I inserted the first cartridge and let it go.  
>Sure enough after about 1100 tape blocks it prompted for another tape.  
>Obviously I'm missing something here, but I'm at a loss as to what I'm 
>doing wrong.  Does anyone have any suggestions, clues, hints, or voodoo 
>chant I can try?

I have this exact same drive but it is mounted on my FreeBSD machine.
When I do a dump on that machine I use dumps -a option which appears
in the man page as follows:

     -a ``auto-size''. Bypass all tape length considerations, and enforce
	writing until an end-of-media indication is returned.  This fits
	best for most modern tape drives.  Use of this option is particu-
	larly recommended when appending to an existing tape, or using a
	tape drive with hardware compression (where you can never be sure
	about the compression ratio).

unfortuneately NetBSD's dump doesn't have this (I just looked at the man
page.) you may have to fiddle with the desity does and such.

let me know if you figure out how to turn on compression.

Christopher R. Bowman
My home page