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Date:      Mon, 3 Feb 2014 22:26:05 +0100
From:      Roland Smith <rsmith@xs4all.nl>
To:        Matthias Apitz <guru@unixarea.de>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: dump(8) && -b option
Message-ID:  <20140203212605.GA49118@slackbox.erewhon.net>
In-Reply-To: <20140203074405.GA10184@sh4-5.1blu.de>
References:  <20140203074405.GA10184@sh4-5.1blu.de>

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On Mon, Feb 03, 2014 at 08:44:05AM +0100, Matthias Apitz wrote:
>=20
> Hello,
>=20
> Last weekend I was playing around with the dump options to improve the
> dump speed to my external USB drive. I tried using the -b option to
> increase the blocksize of the written junks:
>=20
> # dump -0auL -b 100 -f - /usr=20
> ...
>   DUMP: finished in 40 seconds, throughput 7485 KBytes/sec
>=20
> # dump -0auL -b 10 -f - /usr
> ...
>   DUMP: finished in 70 seconds, throughput 4274 KBytes/sec
>=20
> with -b 1000 the dump hangs forever:
>=20
> # dump -0auL -b 1000 -f - /usr
> ...
>   DUMP: dumping (Pass III) [directories]
> (hangs)
>=20
> on of its child is doing this where fd 3 is the device to be backed up:
>=20
> pread(0x3,0x28809000,0x1000,0x89909000,0xa5,0xbfbfcc88) ERR#5 'Input/outp=
ut error'
> pread(0x3,0x28809000,0x1000,0x89909000,0xa5,0xbfbfcc88) ERR#5 'Input/outp=
ut error'
> pread(0x3,0x28809000,0x1000,0x89909000,0xa5,0xbfbfcc88) ERR#5 'Input/outp=
ut error'
> pread(0x3,0x28809000,0x1000,0x89909000,0xa5,0xbfbfcc88) ERR#5 'Input/outp=
ut error'
> pread(0x3,0x28809000,0x1000,0x89909000,0xa5,0xbfbfcc88) ERR#5 'Input/outp=
ut error'
>=20
> Why is this?

Input/output error indicates that a file could not be read. Did you run a f=
sck
before dump?

Are you trying to dump a live filesystem? On 9.0 doing dumps of a live
filesystem that has journaled soft-updates (SU+J) enabled were broken. I am
not sure if this has been fixed already.

> Maybe the best is doing the write to the disk with dd(1), for example
> with
>=20
> # dump -0auL -f - /usr  | dd bs=3D8m > /dev/da0s1a/usr.dmp

For now, the best thing AFAIK is not to use -L but to dump the filesystem f=
rom
single user mode when it is not mounted.

Roland
--=20
R.F.Smith                                   http://rsmith.home.xs4all.nl/
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