I have a JMicron raid controller on the motherboard, and I have a menu in which I can set RAID arrays when the system boots. I've set it to RAID-1 and added my two identical 2TB disks (the OS disk is separate).

In Ubuntu, in the Disk Utility, I could see these 2 hard disks and I could see an additional entry under Peripheral devices which was a 2TB disk. I assumed that this is some sort of a virtual view over my RAID array.

I used the Format Volume option to format (NTFS) the 2TB disk listed under Peripheral devices. It appeared as a mounted device in the /media/data_raid. I've copied most of the files there and it worked fine.

I've rebooted the system, and now I suddenly see an additional 3 disks in peripheral devices, which doesn't make sense. Also, I can no longer mount the /media/data_raid - clicking on it in Gnome yields the following error message.

"One or more block devices are holding /dev/dm-0"

This is how things look in Disk Utility:

the original drive

the newly appeared drive

There are additional 3 entries in /dev/mapper for some reason:

~$ ls -l /dev/mapper
total 0
crw------- 1 root root 10, 236 2012-05-01 20:01 control
lrwxrwxrwx 1 root root       7 2012-05-01 20:15 isw_bjcjaghhjj_DATA -> ../dm-0
lrwxrwxrwx 1 root root       7 2012-05-01 20:01 isw_bjcjaghhjj_DATA1 -> ../dm-1
lrwxrwxrwx 1 root root       7 2012-05-01 20:01 isw_bjcjaghhjj_DATA2 -> ../dm-2
lrwxrwxrwx 1 root root       7 2012-05-01 20:01 isw_bjcjaghhjj_DATA3 -> ../dm-3

Can you help me resolve this issue and obtain access to my RAID array again?

Thank you.


There is no mdadm.conf in /etc/.

In /etc/fstab/:

# /etc/fstab: static file system information.
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    nodev,noexec,nosuid 0       0
# / was on /dev/sda1 during installation
UUID=8e466cac-6543-48dc-aedf-ce378375053b /               ext4    errors=remount-ro 0       1
# swap was on /dev/sda3 during installation
UUID=f80e449c-4212-45e6-939c-f16a55ae8ad5 none            swap    sw              0       0
  • run 'lsof' to fin what is holding dm-0
    – Chris2048
    May 1, 2012 at 21:23
  • can you post things like mdadm.conf and /etc/fstab for reference, thanks.
    – Chris2048
    May 1, 2012 at 21:26


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