Jens Theisen schreef:
Hello Paul,
There are two issues here. [...]
Interesting. But still: Either dump or restore needs to understand the
filesystem so that the TOC can actually be generated into the stream or
from the stream. And presumably one can't restore the data backed up from
one filesystem to a disk with a different filesystem directly.
Dump is indeed filesystem specific. That means indeed that dump for
ext2 is completely different from a dump for ufs or xfs, etc.
And the corresponding restore program is also specific to the output
generated by the dump program. The TOC is therefor generated on
the client itself (because the server could be different OS, not
understanding the dump format for from the client).
But luckily the restore program does not write diskblocks to the raw
device, but uses the normal write() syscalls to restore a file.
That means that, if you have a restore for e.g. ext2fs that can read the
dump files generated, they could be restored to e.g. an xfs filesystem.
I'm not sure what happens with the extended attributes that are in the
dump file, but are not supported in the target filesystem. Anybody
tried that already?
Indeed I found only a dump for ext2fs so far (I'm using Linux).
Dump for ext2 is good for ext3 too, just in case you're in doubt.
Also dump can do incremential dumps. Does it do them filewise or just from
the uninterpreted disk content?
Actualy that is up to the dump program itself, which I did not yet
study in detail. But I believe it does it filewise, also because in
most (all?) filesystem I know, there is no information that indicates
which blocks of a file have changed.
But I can imagine that filesystems would implement that too, considering
the immense size of the current disks and filesystems...
--
Paul Bijnens, Xplanation Tel +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM Fax +32 16 397.512
http://www.xplanation.com/ email: Paul.Bijnens AT xplanation DOT com
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