Raid on linux - re-add a drive



Today, one of the developer of 123Monsite.com mess up with one server, and this lead to this :


They configure fake hardware on the mother board while it's a software raid... noticing it didn't work, they remove a drive to boot on a degraded raid... and try to find what's wrong... that's when I interrupt the massacre

this lead to this :
the partitions of the removed drive was marked as deleted (even if it has been replugged and fake-hardware disabled) :

thomas@dev:~$ sudo mdadm --query --detail /dev/md3
/dev/md3:
Version : 00.90
Creation Time : Thu Sep  4 23:15:23 2008
Raid Level : raid1
Array Size : 73778432 (70.36 GiB 75.55 GB)
Used Dev Size : 73778432 (70.36 GiB 75.55 GB)
Raid Devices : 2
Total Devices : 1
Preferred Minor : 3
Persistence : Superblock is persistent

Update Time : Mon Aug 10 22:45:33 2009
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0

UUID : 6c7f5b4f:27e96317:a44ec9ef:2b057faa
Events : 0.296

Number   Major   Minor   RaidDevice State
0       8        4        0      active sync   /dev/sda4
1       0        0        1      removed


In order to re-activate the missing drive on each mdX I run the following command :

sudo mdadm --manage -a /dev/md3 /dev/sdb4
mdadm: re-added /dev/sdb4


which re-enable the partition of the sdb disk and when needed rebuild of the faulty partition :

thomas@dev:~$ sudo mdadm --query --detail /dev/md3
/dev/md3:
Version : 00.90
Creation Time : Thu Sep  4 23:15:23 2008
Raid Level : raid1
Array Size : 73778432 (70.36 GiB 75.55 GB)
Used Dev Size : 73778432 (70.36 GiB 75.55 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 3
Persistence : Superblock is persistent

Update Time : Mon Aug 10 22:56:35 2009
State : clean, degraded
Active Devices : 1
Working Devices : 2
Failed Devices : 0
Spare Devices : 1

UUID : 6c7f5b4f:27e96317:a44ec9ef:2b057faa
Events : 0.300

Number   Major   Minor   RaidDevice State
0       8        4        0      active sync   /dev/sda4
2       8       20        1      spare rebuilding   /dev/sdb4

thomas@dev:~$ cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md3 : active raid1 sdb4[2] sda4[0]
73778432 blocks [2/1] [U_]
[===>.................]  recovery = 16.8% (12412928/73778432) finish=18.6min speed=54688K/sec

md2 : active raid1 sdb3[1] sda3[0]
4883648 blocks [2/2] [UU]

md1 : active raid1 sda2[0] sdb2[1]
1461824 blocks [2/2] [UU]

md0 : active raid1 sdb1[1] sda1[0]
289024 blocks [2/2] [UU]

unused devices: 

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