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From: Malcolm Kay <malcolm.kay@internode.on.net>
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To: David.Bear@asu.edu, freebsd-questions@freebsd.org
Date: Tue, 16 Dec 2003 19:58:12 +1030
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Subject: Re: multiple dumps to single tape
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On Tue, 16 Dec 2003 10:25, David Bear wrote:
> if I am writing multiple dumps to a single tape, is it wise to have mt
> write a setmark after dumping each file system?

When a process closes the tape device, if any data has been written,
the driver causes a FileMark to be written. If you opened the device
as /dev/nsa0 then mt would write a second FileMark so on reading=20
back you would find a zero length file between consecutive dumps.

(if you use /dev/sa0 then the second FileMark will be written at the=20
beginning of the tape effectively discarding previously written dump)

Malcolm Kay