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Below are some notes on using Linux Software RAID. It's not complete yet of course :)
Marking a damaged disk as failed:
mdadm --manage --set-faulty /dev/md1 /dev/sdd1
Removing the damaged disk from the array:
mdadm /dev/md1 -r /dev/sdd1
Shutdown your system, bring it up into single user mode and partition and format your new disk. Set the partition type as Linux Software RAID autodetect. Of course you need to partition your new disk the same as the previous one. Bring the machine up into it's default runlevel, either by rebooting or by doing init 5 or init 2 depending on your Linux distribution.
Add your new disk to the array:
mdadm /dev/md1 -a /dev/sdd1
Viewing the status of the array (the one shown here is repairing):
[root@host ~]# cat /proc/mdstat Personalities : [raid1] md1 : active raid1 sdc1[2] sdd1[1] 142327744 blocks [2/1] [_U] [==========>..........] recovery = 54.5% (77655168/142327744) finish=65.2min speed=16503K/sec md0 : active raid1 sdb1[1] sda1[0] 142327744 blocks [2/2] [UU] unused devices: <none>
Showing status detail for a particular array:
[root@host ~]# mdadm --detail /dev/md1 /dev/md1: Version : 00.90.01 Creation Time : Sat Jan 13 08:24:54 2007 Raid Level : raid1 Array Size : 142327744 (135.73 GiB 145.74 GB) Device Size : 142327744 (135.73 GiB 145.74 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 1 Persistence : Superblock is persistent Update Time : Wed Aug 27 09:10:48 2008 State : clean, degraded, recovering Active Devices : 1 Working Devices : 2 Failed Devices : 0 Spare Devices : 1 Rebuild Status : 55% complete Number Major Minor RaidDevice State 0 0 0 -1 removed 1 8 49 1 active sync /dev/sdd1 2 8 33 0 spare /dev/sdc1 UUID : cb59fcb5:d61a134b:3e799237:ab0c3b4f Events : 0.25582871
View the Detail of a Particular Disk in an Array:
[root@host ~]# mdadm --examine /dev/sdd1 /dev/sdd1: Magic : a92b4efc Version : 00.90.00 UUID : cb59fcb5:d61a134b:3e799237:ab0c3b4f Creation Time : Sat Jan 13 08:24:54 2007 Raid Level : raid1 Device Size : 142327744 (135.73 GiB 145.74 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 1 Update Time : Wed Aug 27 09:20:10 2008 State : clean Active Devices : 1 Working Devices : 2 Failed Devices : 0 Spare Devices : 1 Checksum : ce0b5011 - correct Events : 0.25583249 Number Major Minor RaidDevice State this 1 8 49 1 active sync /dev/sdd1 0 0 0 0 0 removed 1 1 8 49 1 active sync /dev/sdd1 2 2 8 33 0 spare /dev/sdc1