Date: Tue, 15 Mar 2005 15:32:20 +0000 From: Alex Zbyslaw <xfb52@dial.pipex.com> To: Ludo Koren <lk@tempest.sk> Cc: freebsd-questions@freebsd.org Subject: Re: Backup on DDS-4 tapes Message-ID: <42370004.5060506@dial.pipex.com> In-Reply-To: <200503140938.j2E9c2EM024428@lk.tempest.sk> References: <200503140938.j2E9c2EM024428@lk.tempest.sk>
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Ludo Koren wrote:
># /sbin/dump -Lu0 -B 41943040 -C 32 -f /dev/sa0 /usr
>
>
>
I would guess that your tape drive does hardware compression in which
case the amount of data which fits on a tape is variable. In such a
case you can't tell dump how big the tape is -- I haven't used options
like -B since 1600bpi reel-to-reel tapes, except in my day you specified
how many feet of tape you had :-)
from man dump
-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).
Don't know -L, must be a 5.x thing. Try:
/sbin/dump -Lu0 -a -C 32 -f /dev/sa0 /usr
I use -b 64 as well.
Use cpio/tar at your peril as they may not do devices right and may not understand filesystem flags.
--Alex
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