Reading from a Linux RAID1 disk

James Ewing Cottrell 3rd JECottrell3 at Comcast.NET
Fri Aug 27 23:02:19 BST 2010

  This makes no sense. The whole purpose of a mirror is recovery after 
one side fails. However, the software may
require you to confirm this after the failure occurs. In other words, 
the failure mode might be "freeze totally until the user tells me that 
the disk has failed and assumes responsibility for running with no 
redundancy" rather than "just run with only one half of the mirror".

So I would investigate the mdadm commands to explicitly fail one side of 
the mirror. Things might also be more complicated by the fact that you 
have moved the disk to another host. In otherwords, the old sda now 
became sdb, altho the way I understand MD, it essentially writes its own 
high level labels and UUIDs and doesn't care about physical device 
associations for any longer than the life of this boot.

You might also google for "linux software raid mirror disk failure" 
optionally replacing the first three words with "mdadm".

Good Luck and let us know how this turned out.


On 8/15/2010 4:45 PM, Joe Tseng wrote:
> My old file server (running Fedora 6, software RAID1) finally gave up living
> after we lost our power in the big storm a few weeks back.  When I tried to
> start it back up nothing happened - I guess the power supply is kaput.  I
> want to take contents off one of the RAID1 disks and store it somewhere else
> for the time being.  I plugged the disk into an IDE ->  USB converter and
> plugged into my Ubuntu laptop but it can't read it b/c the disk is marked as
> part of an array.  Is there some way I can read this disk short of
> recreating the RAID1 in another old Linux desktop?
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