Date: Wed, 16 Mar 2005 10:53:45 +0100 (CET) From: Ludo Koren <lk@tempest.sk> To: xfb52@dial.pipex.com Cc: freebsd-questions@freebsd.org Subject: Re: Backup on DDS-4 tapes Message-ID: <200503160953.j2G9rjKR003358@lk.tempest.sk> In-Reply-To: <42370004.5060506@dial.pipex.com> (message from Alex Zbyslaw on Tue, 15 Mar 2005 15:32:20 %2B0000) References: <200503140938.j2E9c2EM024428@lk.tempest.sk> <42370004.5060506@dial.pipex.com>
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>> # /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).
It doesn't help either... The result is the same.
> Don't know -L, must be a 5.x thing. Try:
-L This option is to notify dump that it is dumping a live file sys-
tem. To obtain a consistent dump image, dump takes a snapshot of
the file system in the .snap directory in the root of the
filesystem being dumped and then does a dump of the snapshot.
The snapshot is removed when the dump is complete. If the .snap
directory does not exist in the root of the filesystem being
dumped, the dump will fail. This problem can be corrected by
creating a .snap directory in the root of the filesystem to be
dumped; its owner should be root, its group should be operator,
and its mode should be 0770.
> /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
lk
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