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I have a SW RAID 1 with 3 partitions and one of them seem not to be able to re-sync after a HDD failure/replacement.

Here's some info:

more /proc/mdstat 
Personalities : [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
md2 : active raid1 sdb3[1] sda3[2]
      2862630207 blocks super 1.2 [2/2] [UU]

md1 : active raid1 sdb2[1] sda2[2]
      524276 blocks super 1.2 [2/2] [UU]

md0 : active raid1 sda1[2](F) sdb1[1]
      67107768 blocks super 1.2 [2/1] [_U]

unused devices: <none>

I tried to set as faulty /dev/sda1 and then remove it but I get an error, please see below:

# mdadm --manage --set-faulty /dev/md0 /dev/sda1
mdadm: set /dev/sda1 faulty in /dev/md0
# mdadm --manage --remove /dev/md0 /dev/sda1
mdadm: hot remove failed for /dev/sda1: Device or resource busy

Do you have any suggestions on what else I may try?

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Why are you trying to remove a failed drive? It already failed, shut down (if possible, avoids unplanned shutdowns if you pull the wrong drive) and pull the failed drive.

Add the new as a hot spare and it will rebuild.

I know that this brings down the other two raids, but if you have a failure on partition 1 of a drive, it's only a matter of time before the drive goes completely. You need to rebuild all three raids.

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Actually, if the LSR had kicked a drive out, it didn't mean it would be faulty for real, it could be some controllers' hardware glitches. Especially in case when other partitions of the drive are still in the game. So, I'd recommend just trying to add it again. – poige Sep 26 '12 at 22:14
up vote 0 down vote accepted

I only solved this problem by reinstalling the system.

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