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Old 03-13-2009, 08:14 AM   #1
Tahir Saleh
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Unhappy RAID6 File System Question.


My question is the RAID6's file system has the same recovery procedure as any file system. The problem is i have to recover data from a partially formatted RAID6's file system.

Last edited by Tahir Saleh; 03-13-2009 at 11:15 AM.
 
Old 03-13-2009, 11:33 AM   #2
mesiol
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Hi,

RAID6 isn't a file system. It's a technology to distribute data over various disks having checksums to recover from disk error.

What is "recovery procedure as any filesystem". What means "partially formatted" exactly from your point of view?

Could you please provide detailed setup and problem information.
 
Old 03-13-2009, 12:39 PM   #3
Dankles
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Yes, is this a software or hardwaer RAID? How many drives are in the RAID? Can you still access the data? What is telling you that there is an error?
Version of kernel and Distro info would be nice too.
 
Old 03-13-2009, 02:17 PM   #4
rweaver
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Quote:
Originally Posted by Tahir Saleh View Post
My question is the RAID6's file system has the same recovery procedure as any file system. The problem is i have to recover data from a partially formatted RAID6's file system.
I'm really not quite sure what you're asking exactly.

Data recovery on a RAID drive functions generally exactly like data recovery on a non-RAID drive.

You can't recover all the data from a single drive unless you're doing mirroring.

What do you mean "partially formatted"? Did you start formatting the file system and stop half way through because you picked the wrong device?

If you destroyed a single disk in the array (say by formatting /dev/sda3 directly) you might be able to remove that disk and put a bank one back.

If you actually formatted the array directly... you're more or a less screwed unless your data can be recovered with something like ext3grep, foremost, or tsk (or whatever tools are applicable for your fs).

Backups are important even when you have raid.

Last edited by rweaver; 03-13-2009 at 02:20 PM.
 
Old 03-14-2009, 08:23 AM   #5
Tahir Saleh
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The situation is that the LVM2 was made on a machine. OS specification is as follows:
Distro = RHEL4
Kernel = 2.6.9-5.ELsmp

Now what has happened is that eight hardware RAID6 disk four (/dev/sda,/dev/sdb,/dev/sdc, /dev/sdd) on one side and four on the other side (/dev/sde,/dev/sdf,/dev/sdg, /dev/sdh) were combined to form an LVM2 partitions such that each side were made to be /dev/vg01/lvol0 and /dev/vg02/lvol0 by the commands:

#lvcreate -name lvol0 --size 8T vg01
#lvcreate -name lvol0 --size 8T vg02


Now there was also an entry in /etc/fstab:

/dev/vg01/lvol0 /var/export1 ext3 rw,noatime 0 0
/dev/vg02/lvol0 /var/export2 ext3 rw,noatime 0 0

where /var/export1 and /var/export2 are directories created with mkdir command.

Problem:

The device /dev/sda has accidentally been partially formatted i.e. I started formatting the file system of device /dev/sda and stopped half way through because I had picked the wrong device. It was approximately 15% formatted. Destro did not boot after that.

Progress so Far:

Destro was recovered by commenting the entries from /etc/fstab.



By removing that disk and putting a blank one back will to it i.e. will it recover the data. Can LVM be recovered.

Regards.

Last edited by Tahir Saleh; 03-14-2009 at 08:38 AM.
 
Old 03-22-2009, 01:53 AM   #6
mesiol
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Hi,

i am already not sure if i understand you correctly.

You formatted one of the underlying hardware RAID disks? This means one of your LVM disks is dead. LVM works as long as all underlying disks are available and have existing LVM information. In your case, there seems to be no useful information on your disks /dev/sda, what means LVM is unable to create the VG.
 
  


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