Software Raid Array???

[phillips321]

Hi guys,

Just got 3 extra drives for my machine.
2x160Gb sata
1x 165Gb sata

How do i create a raid0 array of these drives?

On each drive i have got a partition whose size is 160GB and formatted to type fd (Raid Autodetect)

i have tried the following:

mdadm --create /dev/md0 --level=0 --raid-devices=3 /dev/sdb1 /dev/sdc1 /dev/sda1
mkfs.ext4 /dev/md0
mount /dev/md0 /media/raid

but for some reason it doesnt work.

Also another issue.
the drives do not always have the same device

sometimes the 3 drives are /dev/sdA /dev/sdB and /dev/sdC
... and other times /dev/sdB /dev/sdC and /dev/sdD

any ideas?

Cheers

P.s. is it ok to raid partitions rather than drives?

[deconstrained]

You need to assemble it first before you can use it;

# mdadm --assemble /dev/md0 /dev/sdb1 /dev/sdc1 /dev/sda1

With regard to the devices not getting the same kernel names on reboots: you should just use the UUID of the array instead of the kernel names (sdb1, sdc1 etc). Pick one of the partitions in the array (i.e. sdb1) and the 'blkid' command command will print information from the superblock, including the UUID (and TYPE="linux_raid_member"). That UUID is common to all the devices in the array and can be used by the kernel and mdadm to assemble the array. Then you can use

# mdadm --assemble --uuid=[uuid] /dev/md0
To assemble your array at boot time: first assemble the arrays you want to have ready at boot time, then

# mdadm --detail --scan >> /etc/mdadm/mdadm.conf
To be on the safe side, open it with a text editor and make sure that only the arrays you want to assemble are in that file (and remove duplicate entries, if any). Then, rebuild your Linux image:

# update-initramfs -k all -c

If you're having trouble assembling/mounting, make sure the appropriate module (raid1 in your case) is modprobe'd into the kernel, and fsck.ext4 the volume before mounting (fsck is generally a good idea to do before mounting filesystems). Also, paying close attention to (and sharing) the error messages would help diagnose the problem.

Good luck!

[phillips321]

root@DesktopUbuntu:~# blkid
/dev/sda1: UUID="10e4ff63-3613-43f2-a2d5-049785634c64" TYPE="swap"
/dev/sda2: UUID="1E223B59223B355D" TYPE="ntfs"
/dev/sda3: LABEL="DATA" UUID="2357075637B4BD39" TYPE="ntfs"
/dev/sda4: LABEL="Linux" UUID="71fa4d16-5b8d-4e2f-921f-54e09e372905" TYPE="ext4"
/dev/sdb2: UUID="ca8f0f27-1431-4b75-a16c-cb445fdf0a9e" TYPE="swap"
/dev/sdd1: UUID="48e267f3-e526-b907-393f-3ca1cbed4451" TYPE="linux_raid_member"
/dev/sdc1: UUID="48e267f3-e526-b907-393f-3ca1cbed4451" TYPE="linux_raid_member"
/dev/sde1: LABEL="backup500" UUID="4caffe8f-24e2-48ff-9707-10f1391c934a" TYPE="ext4"


Hmmm, /dev/sdb1 doesn't show up?


root@DesktopUbuntu:~# fdisk -l

Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000cdc1b

Device Boot Start End Blocks Id System
/dev/sda1 1 124 995998+ 82 Linux swap / Solaris
/dev/sda2 125 24439 195310237+ 7 HPFS/NTFS
/dev/sda3 * 36620 121601 682617915 7 HPFS/NTFS
/dev/sda4 24440 36619 97835850 83 Linux

Partition table entries are not in disk order

Disk /dev/sdb: 164.7 GB, 164696555520 bytes
255 heads, 63 sectors/track, 20023 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000524fa

Device Boot Start End Blocks Id System
/dev/sdb1 567 20023 156288352+ fd Linux RAID autodetect
/dev/sdb2 1 566 4546363+ 82 Linux swap / Solaris

Partition table entries are not in disk order

Disk /dev/sdd: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00031fed

Device Boot Start End Blocks Id System
/dev/sdd1 1 19457 156288321 fd Linux RAID autodetect

Disk /dev/sdc: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00010c9d

Device Boot Start End Blocks Id System
/dev/sdc1 1 19457 156288321 fd Linux RAID autodetect

Disk /dev/sde: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x05a569de

Device Boot Start End Blocks Id System
/dev/sde1 1 60801 488384001 83 Linux

[deconstrained]

Explicitly specify which block device to examine; blkid /dev/sdb1.

Just FYI, sometimes the Ubuntu flavor (default configuration) of mdadm can play mind games with you. This is because dpkg adds an initscript and starts mdadm as a service BY DEFAULT, and it auto-detects and assembles stuff without you knowing about it or explicitly commanding it, which then results in various block devices being "busy" when they shouldn't be - in short, it thinks it's smart enough to work without your instruction, but in actuality, it's really dumb (and it's pissed me off times aplenty).

Something you could try is stopping mdadm (/etc/init.d/mdadm stop and/or pkill -SIGKILL mdadm), disassembling ALL the arrays (for d in /dev/md*; do mdadm --misc -S $d; done) and then starting over.

[phillips321]

bklid directed at the device doesnt give any output:

root@DesktopUbuntu:~# blkid /dev/sdb1
root@DesktopUbuntu:~#


This is starting to confuse me a great deal now....

[deconstrained]

The reason you cannot see sdb1 may be because mdadm has auto-assembled a half-assed array involving it, so that would make the block device unavailable.

Like I said, it's most likely that mdadm is running as a service and playing mind games with you. KILL IT WITH FIRE, stop all your "md" devices, and then try reassembling.

Also, if you rebooted since your last attempt, udev may have reassigned device names (i.e. sda,sdb,sdc) in a different order.