Also Sprach Christoph Scheeder:
> Hi,
> if i read this statement of Linus correct the only thing he is saying
> is:
>
> don't run dump on a filesystem which could be active.
>
> That isn't realy new.
>
> it is known very well that dump has problems with active filesystems,
> as it bypasses the normal way data gets read and written to disk.
>
> If you need a dump image to be nearly 100% reliable you have to mount
> the filesystem readonly or to unmount it completly before doing the
> dump.
> Only then you can be shure all caches have been flushed to disk, and
> nobody will overwrite data while it gets backuped.
>
> if someone goes the the so called normal way and runs dump on a
> read/write
> mounted filesystem he is indeed playing a dangerous game if he trusts
> his
> backup without verifying all needed data is in the dump.
>
> so Linus oppinion is completly correct.
>
> using a program for a purpose it is not designed for is dangerous and
> might fail.
>
> if you need to backup an active filesystem use a program like tar
> which is designed to do that.
>
> Christoph
>
I use both vendor dump and GNU tar, the former for platform specific
partitions like /usr, /opt and the latter for data. I don't think either
tar or dump are meant to deal with active filesystems, especially ones
which are highly active.
Isn't the issue here that if you run dump on an active filesystem
it will back up an inconsistent image possibly w/o notification whereas tar
will usually give up on an active file and emit an error message?
Since I use dump to back up system partitions, I don't think an
inconsistent image is a problem with my use of dump, because the changes
are occurring in /var/spool or /var/tmp. And I want tar to fail
rather than create an inconsistent file because of the nature of the data.
I've seen ads for the commercial and pricey backup packages from
Syncsoft, Veritas and so on which claim no problems with live backups
on *nix or NT. I suppose they have some way of write-locking files,
copy to memory, then releasing the lock, but how could these utils
work at the block rather than file level?
--
C. Chan < [EMAIL PROTECTED] >
Finger [EMAIL PROTECTED] for PGP public key.
