software raid

When I run the following command at shell prompt on Debian or Ubuntu Linux

mdadm -Ac partitions /dev/md0 -m dev

I’m getting the message/warning that read as follows:

Failed to RUN_ARRAY /dev/md0 invalid argument.

How do I fix this issue? How do I rebuild array again on Linux operating system using mdadm command?

Tutorial details
Difficulty level Easy
Root privileges Yes
Requirements None
Est. reading time 5m
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Q. I have two disk-mirrored array, suppose if one of my disk in mirrored RAID array fails, then I will replace that disk with new one (I have hot swapping SCSI drives). Now question is how I rebuild a RAID array after a disk fails.

A. A redundant array of inexpensive disks, (redundant array of independent disks) is a system, which uses multiple hard drives to share or replicate data among the drives. You can use both IDE and SCSI disk for mirroring.

If you are not using hot swapping drives then you need to shutdown server. Once hard disk has been replaced to system, you need to use used raidhotadd to add disks from RAID-1, -4 and -5 arrays, while they are active.

Assuming that new SCSI disk is /dev/sdb, type the following command:# raidhotadd /dev/mdX /dev/sdbReplace /dev/mdX with actual raid device name (e.g. /dev/md0). While array is under construction, you can see progress and other information by typing following command:# cat /proc/mdstat

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