mdadm is a tool designed to replace raidtools under GNU/Linux.
Linux with md devices support and RAID 1 support.
| Task | Command |
|---|---|
| Create a new mirror | mdadm -C -n 2 -l 1 /dev/md0 /dev/sda /dev/sdb |
| Verify mirror status | mdadm –detail /dev/md0 |
| Hot remove a drive | mdadm –manage -r /dev/md0 /dev/sda |
| Hot add a drive | mdadm –manage -a /dev/md0 /dev/sda |
| Simulating a faulty disk | mdadm –manage /dev/md0 –set-faulty /dev/sda |
If a disk fails, you should replace the disk and tell Linux to resync the array. First, you'll need to identify the faulty disk. (using the dmesg for example)
Then, you should stop the Linux host, and replace the faulty disk. Once the disks is changed, restart the host.
Now, you should reintegrate the new disk to the array:
(note: you should replace sdc and md1 with correct values you've identified before)
#> mdadm --manage /dev/md1 -r /dev/sdc #> mdadm --manage /dev/md1 -a /dev/sdc
Now, enjoy reconstruction !
You could get informed on sync status:
#> mdadm --detail /dev/md1
Sample output:
/dev/md1:
Version : 00.90.01
Creation Time : Thu Mar 23 23:09:39 2006
Raid Level : raid1
Array Size : 160086464 (152.67 GiB 163.93 GB)
Device Size : 160086464 (152.67 GiB 163.93 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 1
Persistence : Superblock is persistent
Update Time : Fri Mar 24 06:56:27 2006
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
UUID : 6965fc49:6b5790d8:2ca8dc68:1afb7fbd
Events : 0.14319
Number Major Minor RaidDevice State
0 8 32 0 active sync /dev/sdc
1 8 48 1 active sync /dev/sdd
mdadm has an optional config file, which could be used to specify less informations on the command line.
Sample config file:
DEVICE partitions ARRAY /dev/md0 level=raid1 num-devices=2 devices=/dev/sda1,/dev/sdb1 ARRAY /dev/md1 level=raid1 num-devices=2 devices=/dev/sdc1,/dev/sdd1 MAILADDR your@mail.to.be.informed.in.case.of.disk.failure