Cloning 1 hard disk in a software RAID

[Colin Law]

2009/7/28 Liam Proven <lproven at gmail.com>:
> 2009/7/28 Colin Law <clanlaw at googlemail.com>:
>> 2009/7/28 Liam Proven <lproven at gmail.com>:
>>> 2009/7/28 Alvin Chang <alvin.chang at gmail.com>:
>>>> On Tue, Jul 28, 2009 at 16:20, Liam Proven <lproven at gmail.com> wrote:
>>>>>
>>>>> I have a degraded & rather unstable software RAID on my server. 1 disk
>>>>> does not register at all any more & the md subsystem won't mount it as
>>>>> being "stale". Another sometimes mounts but won't stay up for long.
>>>>
>>>> What does cat /proc/mdstat say? Which RAID level is it?
>>>>
>>>>>
>>>>> <snip>
>>>>> dd if=/dev/sdd of=/dev/sde
>>>>>
>>>>> to copy the whole of the unstable drive onto a new one.
>>>>>
>>>>> Should this work, or is it a disastrously bad idea or something?
>>>>
>>>> Well, that really depends... if the source drive is broken, you might need
>>>> to use something other than dd to clone the disk so that it ignores bad
>>>> sectors, e.g. Gohst 4 Linux...
>>>
>>> I don't think I have any bad blocks, it just won't always spin up.
>>>
>>>> In fact, if you are using RAID5 or above... simply re-initialize the array
>>>> with a working blank drive should do the trick.
>>>
>>> Tried that; nothing seems to happen & this is the only copy of the
>>> data that I have so I am wary of experimenting too much...
>>
>> I am sure will already have done this but backup the _really_
>> important stuff onto CD or another machine or something before doing
>> anything else
>
> I can't, the array won't stay up long enough... Thus the last-ditch
> efforts to try to get some stuff off the blasted thing.
>

I don't know much about RAID so this may be a silly suggestion.  Could
you take the sometimes working disk out and plug it in to a different
PC (or the same one) as a single disk rather than part of the RAID
set?  Or can it not work on its own?  Not that this will help if the
disk won't keep going.

Colin