I'm trying to set up a RAID1 partition on my Ubuntu 9.10 workstation.
On this dual-boot system, Ubuntu is running from a separate drive (/dev/sdc
- an SSD that is quite small, which is why I need more disk space). Besides that, there are two traditional 500 GB hard drives, which have Windows 7 installed (I want to keep the Windows installation intact), and about half of the space unallocated. This space is where I want to set up a single, large RAID1 partition for Linux.
(This, to my understanding, would be software RAID, whereas the Windows partitions are on hardware RAID - I hope this isn't a problem... Edit: See Peter's comment. I guess this shouldn't be a problem since I see both drives separately on Linux.)
On both disks, /dev/sda
and /dev/sdb
, I created, using fdisk, identical new partitions of type "Linux raid autodetect" to fill up the unallocated space.
Device Boot Start End Blocks Id System
/dev/sda1 1 10 80293+ de Dell Utility
/dev/sda2 * 11 106 768000 7 HPFS/NTFS
Partition 2 does not end on cylinder boundary.
/dev/sda3 106 30787 246439936 7 HPFS/NTFS
/dev/sda4 30787 60801 241095200+ fd Linux raid autodetect
So, I would like to create a RAID array from /dev/sda4 and /dev/sdb4 using mdadm
. But I don't seem to get it working:
$ sudo mdadm -Cv /dev/md0 -l1 -n2 /dev/sd{a,b}4
mdadm: Cannot open /dev/sda4: Device or resource busy
mdadm: Cannot open /dev/sdb4: Device or resource busy
mdadm: create aborted
After booting the machine, the same command yields:
$ sudo mdadm -Cv /dev/md0 -l1 -n2 /dev/sda4 /dev/sdb4
mdadm: Cannot open /dev/sda4: No such file or directory
mdadm: Cannot open /dev/sdb4: No such file or directory
So now it seems that the devices are not automatically detected in boot... Using fdisk both sda
and sdb
still look correct though.
Edit: After another reboot the devices are back:
$ ls /dev/sd*
/dev/sda /dev/sda2 /dev/sda4 /dev/sdb1 /dev/sdb3 /dev/sdc /dev/sdc2
/dev/sda1 /dev/sda3 /dev/sdb /dev/sdb2 /dev/sdb4 /dev/sdc1 /dev/sdc5
But so is "Device or resource busy" when trying to create the RAID array. Quite strange. Any help would be appreciated!
Update: Could the device mapper have something to do with this? How do /dev/mapper
and dmraid
relate to all this mdadm
stuff anyway? Both provide software RAID, but.. differently? Sorry for my ignorance here.
Under /dev/mapper/
there are some device files that, I think, somehow match the 3 Windows RAID partitions (sd{a,b}1 through sd{a,b}3). I don't know why there are four of these arrays though.
$ ls /dev/mapper/
control isw_dgjjcdcegc_ARRAY1 isw_dgjjcdcegc_ARRAY3
isw_dgjjcdcegc_ARRAY isw_dgjjcdcegc_ARRAY2
Resolution: It was the mdadm Wikipedia article that pushed me in the right direction. I posted details on how I got everything working in this answer.
/dev/sda
and/dev/sdb
as separate drives.