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
Tanniel Simonian schrieb:
>
> Anyone read from the kernel.org newsgroup a message from Linus Torvald
> about dump?
>
> here is his message:
>
> "Note that dump simply won't work reliably at all even in 2.4.x: the
> buffer cache and the page cache (where all the actual data is) are not
> coherent. This is only going to get even worse in 2.5.x, when the
> directories are moved into the page cache as well."
>
> "So anybody who depends on "dump" getting backups right is already playing
> russian rulette with their backups. It's not at all guaranteed to get the
> right results - you may end up having stale data in the buffer cache that
> ends up being "backed up"."
>
> "Right now, the cpio/tar/xxx solutions are definitely the best ones, and
> will work on multiple filesystems (another limitation of "dump"). Whatever
> problems they have, they are still better than the _guaranteed_(*) data
> corruptions of "dump"."
>
> "Dump was a stupid program in the first place. Leave it Behind"
>
> He then finally notes:
>
> (*) Dump may work fine for you a thousand times. But it _will_ fail under
> the right circumstances. And there is nothing you can do about it.
>
> ----------------------------------------
>
> okay I've run dump THOUSANDS + 1 times, but have yet to have a problem
> with Amanda and especially restores. It has saved my ass repeatedly,
> especially when a hard disk has failed and everything has been running
> from memory for days.
>
> So please I need opinions. I've already rigged amanda to work with my
> exabyte EZ17 drive. I don't think I can rig it anymore to work with Tar.
>
> latz,
>
> Tanniel Simonian
> Programmer Analyst III
> University of California Riverside, Libraries.
