[SATLUG] RAID5 Recovery - Reassembly Questions #2

Samuel Leon satlug at net153.net
Wed Aug 26 21:51:42 CDT 2009

David Labens wrote:
> Do I need to issue the command in any order?  Or will it figure it out?
> David Labens
No the order of the disks to assemble does not matter.  And make sure 
everything is connected because once you force assemble you will have to 
add the drive that it left out.

I attached a copy of the guide I wrote earlier:

 > Here is an updated guide for the next steps:
 > First make sure that the raid superblocks are the same for both the old
 > and new drive:
 > mdadm --examine /dev/sda /dev/sdb
 > Then shutdown, reconnect everything and bring the computer up.  Might
 > also make sure that all your disks are linked to the right device names
 > as needed (sda,sdb ect)
 > then force the array to reassemble:
 > mdadm --assemble --force /dev/md0 /dev/sde1 /dev/sda1 /dev/sdb1 /dev/sdc1
 > (make sure those drive numbers are right, I copied them from an earlier
 > post. Also, if you don't get some output saying that the array *has been
 > started* then you need to stop right here.  The output you should get
 > should be similar to:
 > mdadm: forcing event count in /dev/hdd1(2) from 228 upto 232
 > mdadm: clearing FAULTY flag for device 1 in /dev/md0 for /dev/hdd1
 > mdadm: /dev/md0 has been started with 2 drives (out of 3).
 > )
 > That should bring it up in degraded mode with one failed drive. So 
then do:
 > mdadm -D /dev/md0
 > and that will list some info and at the bottom you will see what drive
 > is still removed.  So add it to the array with:
 > mdadm --add /dev/md0 /dev/sdX
 > but if there is still more than one drive missing from the array at this
 > point never use mdadm --add because something is wrong and that will
 > make it worse.
 > If added correctly, the array should start to resync.  Let it finish and
 >  make sure the filesystem on /dev/md0 stays unmounted.  Once it is done
 > resyncing check the filesystem (if it is ext3) with:
 > e2fsck -D -f /dev/md0
 > You will probably get some errors and have to press "y" a hundred times.
 > Any files that are lost will be put in your lost+found folder and will
 > be given their inode number as the file name.
 > Then you can mount the filesystem on /dev/md0. Then you should be done.

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