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Date:      Wed, 08 May 2002 22:34:21 -0700
From:      paul beard <paulbeard@mac.com>
To:        stable@FreeBSD.ORG
Subject:   Re: question on dump(8) and SCSI tape drive
Message-ID:  <3CDA0A5D.6070803@mac.com>
References:  <Pine.A41.3.96.1020509012335.107124B-100000@cortez.sss.rpi.edu>

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Lawrence S. Lansing wrote:
>>I just installed a DDS-2 tape drive (Archive/Seagate Peregrine 
>>with HW compression) and want to do some backups. From what I can 
>>tell, a 120m tape should hold 4 Gb of uncompressed data and 8 Gb 
>>compressed. I'm puzzled why dump(8) wants 2 tapes to backup 77+ Mb 
>>of data (the / partition below) and 44% of a tape for /var (16 Mb).
>>
>>   DUMP: estimated 77567 tape blocks on 1.99 tape(s).
> 
> 
> What flags are you giving "dump"?  What's the command line you are typing?
> I give dump the -a flag:
> 
>    -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 particularly 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).
> 
> -Larry Lansing

That's what I was thinking was the problem (I couldn't make out 
how dump figured out 44% of what?).

Thanks: things seem to be moving more smoothly now.

-- 
Paul Beard
8040 27th Ave NE
Seattle WA 98115
206 529 8400

The economy depends about as much on economists as the weather does on
weather forecasters.
		-- Jean-Paul Kauffmann


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