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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.

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Is this a fresh installation of 12.04 or did it already work with this version? Because I had problems with my RAID too, after first boot. – Bevor May 1 '12 at 19:24
This is Ubuntu 11.10. I did not update to 12.04 yet. – axel22 May 1 '12 at 19:33
@Bevor: What did you have to do with 12.04? – Kyle Brandt May 2 '12 at 18:54
@KyleBrandt That was my problem:… – Bevor May 2 '12 at 19:20

I have the exact same issue, trying to partition/format two 2TB RAID0 disks. I'm running hardware raid set in bios because I've read it's faster than software raid and doesn't load the CPU as software raid does.

I installed GParted and with that I could make a partition and format the RAID disks.

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