[CentOS] A questiong about replacing my failing drive

Dag Wieers dag at wieers.com
Sun Jun 12 20:39:11 UTC 2005


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 at wieers.com,  http://dag.wieers.com/   --
[all I want is a warm bed and a kind word and unlimited power]



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