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Re: how to reconstruct MD RAID device?

On (24/08/05 16:31), Jukka Salmi wrote:
> Clive Menzies --> debian-user (2005-08-24 15:08:11 +0100):
> > Have you tried something like:
> > 
> > $ mdadm /dev/md2 -a /dev/hdb3
> No. Unfortunately it's a production system, hence I'm a little bit
> cautious with "trying" things... So, considering md2 is used as the
> root file system device, is adding hdb3 to it as you describe dangerous?
> What exactly does this command do? Does it also start reconstruction
> onto hdb3? As you notice, I'm not familiar with Linux software RAID
> at all...

Well, I'm no expert and I can understand your reluctance to experiment.

It's been a while since I set up 3 RAID servers but I did find the
following links helpful:
# http://rootraiddoc.alioth.debian.org/
# http://juerd.nl/site.plp/debianraid
# http://xtronics.com/reference/SATA-RAID-Debian.htm

As I understand it, adding hdb3 to the /dev/md2 will reassemble the
array; however, if hdb3 has become corrupted in some way, it may fail if
it can't recover but this should have no adverse impact on hda3.

You have a number of options:

- boot from a live CD (ubuntu or the like) and see what that
produces; I seem to recall that it will attempt to recognise and start
any RAID devices

- e2fsck hdb3 and then try to reassembe the array (in addition to --add
there is --assemble in the man page, which may be more suitable) ; if
that fails, you could reformat the partition with mkfs.

- buy a new disk (same size) and swap it for hdb and reassemble all the

I read on the list recently, someone removed the mdadm.conf file and
rebooted which solved their problem with initialising arrays; might be
worth googling for that.

Sorry not to be more confident in my advice but it is probably what I
would do.


www.clivemenzies.co.uk ...
...strategies for business

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