On Sun, 12 Jun 2005, Rodrigo Barbosa wrote:
On Sun, Jun 12, 2005 at 03:45:19AM +0200, Dag Wieers wrote:
Check my other post regarding this. Dump won't clone wholedisks. It will clone filesystems (with all metadata intact).
The problem with a broken disk is that your filesystem may not be correct. And you can't do a fsck to correct the inconsistencies because the disk is not reliable.
That's why you require something like ddrescue, so you can copy everything that is still accessible and fill the blank spaces in with zero-blocks. So it doesn't abort or truncate the output like dd, maybe dd conv=noerror is similar but ddrescue has other features like proper status info during copying and decreasing blocksize when blocks fail to be read.
I never tried ddrescue, so I can't comment.
But, as far as I remember, dump will only abort if you get an error on the writing side. Memory can be at fault here, tho.
But dump expects that your filesystem can be trusted, that it is still consistent. Which, if you have a broken disk, is not (necessarily) the case.
I'm not talking about a backup mechanism, I'm sure dump has its use. But when you have a failing drive (which was the topic) you better not use something that expects a working filesystem and you most certainly want to recover your filesystem on the broken disk (fsck).
BTW An example of a broken filesystem could be that directories appear to be missing or filled with garbage. Recursively scanning through the filesystem could yield unexpected results.
-- dag wieers, dag@wieers.com, http://dag.wieers.com/ -- [all I want is a warm bed and a kind word and unlimited power]