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Re: [opensuse] Quirky software RAID1 Question - Howto mount 1 drive on another machine?
  • From: "David C. Rankin" <drankinatty@xxxxxxxxxxxxxxxxxx>
  • Date: Sun, 12 Apr 2009 19:28:28 -0500
  • Message-id: <49E2872C.2080702@xxxxxxxxxxxxxxxxxx>
brian@xxxxxxxxx wrote:
Quoting "David C. Rankin" <drankinatty@xxxxxxxxxxxxxxxxxx>:


I have a quandary. I had two Seagate 750G drives in a software raid on
A. I needed to remove one of the drives and RMA it due to excessive
head schizophrenia. I now have the device out of the box to RMA but I need to
mount it to delete some of the data. I tried mounting is via usb, but
an error due to raid as the file type:

[23:03 alchemy:/home/david/linux/packages/SRPMS] # mount /dev/sdb1 /mnt/750
mount: unknown filesystem type 'linux_raid_member'

So next I decided to create a temporary md0 on my laptop and add one
the array. No dice:

[23:06 alchemy:/home/david/linux/packages/SRPMS] # mdadm --create /dev/md0
--level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1
mdadm: /dev/sdb1 appears to contain an ext2fs file system
size=732571864K mtime=Fri Apr 3 20:21:45 2009
mdadm: /dev/sdb1 appears to be part of a raid array:
level=raid1 devices=2 ctime=Fri Mar 27 15:38:36 2009
mdadm: Cannot open /dev/sdc1: No such file or directory
mdadm: create aborted


OK maybe:

[23:03 alchemy:/home/david/linux/packages/SRPMS] # mdadm --create /dev/md0
--level=1 --raid-devices=1 /dev/sdb1
mdadm: '1' is an unusual number of drives for an array, so it is probably
a mistake. If you really mean it you will need to specify --force
setting the number of drives.

Again no joy!

Well, how to skin this cat, there must be an easy way, but obviously I'm
struggling with it. What say the RAID gurus?

You don't need to mount the device to erase it.
dd if=/dev/zero of=/dev/sdb bs=4M
and for a 750G drive, come back in a coupkle hours.
you can monitor it's progress by "ps -ef |grep sdb" and get the pid of dd, say
it's 3405
then "while kill -USR1 3405 ;do sleep 1 ;done"

But setting that aside,
I think what you need to do is merely assemble the array, and with the word
missing in place of the non-present devices.

mdadm -A /dev/md9 /dev/sdb1 missing
mkdir /md9
mount /dev/md9 /md9

Untested, and assumes /dev/sdb1 contains a mdraid superblock to fill in all
details left unspecified on the mdadm command line.


Thank you! That's a keeper.

Since I had just purchased the pair of 750G drives, I didn't have a
whole lot
on it, nothing sensitive that for sure. The bulk of the information was a
backup of all the 11.0 and 11.1 rpms from cached rpms. So my final decision was
to delete all family photos, etc, leave all the rpm and send the drive back
with the mdraid superblock in place. If there is anyone working there that
deceptively tries to browse data on returned disks, I wanted to at least make
them scratch their heads for a while ;-)

David C. Rankin, J.D.,P.E.
Rankin Law Firm, PLLC
510 Ochiltree Street
Nacogdoches, Texas 75961
Telephone: (936) 715-9333
Facsimile: (936) 715-9339
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