Unable to create software raid device (Solution)

Woody2143 · n00b Joined: 26 Mar 2003 Posts: 19 Location: Atlanta, GA

I ran in to this today and since I was unable to find an answer I figured I would post one.

I was previously using the fake-raid provided by the bios. After running in to a couple of problems and banging my head against the table I decided to use the software raid with better control.

I was attempting to create the /dev/md1 device per the instructions and kept running in to the error:

# mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1
mdadm: device /dev/sdb1 not suitable for any style of array

After some looking I found that adding --verbose gave me a better idea of the problem:
# mdadm --verbose --create /dev/md1 --level=1 --raid-devices=2 /dev/hdb1 /dev/hdd1
mdadm: super0.90 cannot open /dev/hdb1: Device or resource busy
mdadm: super1.x cannot open /dev/hdb1: Device or resource busy
mdadm: ddf: Cannot use /dev/hdb1: Device or resource busy
mdadm: Cannot use /dev/hdb1: It is busy
mdadm: device /dev/hdb1 not suitable for any style of array

I ran 'lsof' but was unable to find anything using my device.

I then got to thinking that despite removing the software raid in the bios it was still on the OS.

I checked dmtab but nothing was in there so I ran 'dmsetup table' and sure enough a device was still listed.

I used 'dmsetup remove sil_ajadaccdfcac' and the device was deleted.

After that it let me create the md device.

I hope this helps out should someone else run in to this problem.
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-- Woody2143

richard.scott · Posted: Tue Mar 23, 2010 2:01 pm Post subject:

it sounds like you already have your device mounted... or in use by the fake raid.

What kernel boot options did you provide? you won't easily be able to convert a fake raid system to a software raid system while its running.
You'd need to make a backup (just in case) and boot from a LiveCD to create the mirror.

Rich

Woody2143 · n00b Joined: 26 Mar 2003 Posts: 19 Location: Atlanta, GA

the_mgt · Posted: Sun May 02, 2010 6:46 pm Post subject:

Have you converted the raid from dm to md with all the data on the partitions? And it did work as in "all data is safe"?

I am trying to get rid of my dm in favour of md, too. (Of course i will do a full backup, but I am curious if it is that simple!)

edit: typo? is it "safe" or "save"? :roll:

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richard.scott · Posted: Tue May 04, 2010 9:32 am Post subject:

I don't think you can do that as the md device is a layer between the filesystem and the disk
dm just duplicates the filesystem, and works at a higher level to md.

Your best bet will be to backup your data and start from scratch.

Rich
p.s. its safe