[dm-devel] Backing up the snapshot volume...

[Manu Tayal]

Hi,
I have created a snapshot using EVMS. I was able to mount the same. I want to
take a block level backup of the snapshot volume i.e. I want to create a new
device and dump the snapshot volume onto it. I tried doing so by:
	dd if=<snapshot device> of=<Newly created partition say, /dev/hdb2>
bs=1024

But this gave me a bunch of errors: 

	end_request: I/O error, dev 03:40 (hdb), sector 22423
	hdb: dma_intr: status=0x51 { DriveReady SeekComplete Error }
	hdb: dma_intr: error=0x40 { UncorrectableError }, LBAsect=22425,
sector=22425

This kept repeating for a lot of sector numbers.
After this I was able to mount /dev/hdb2 onto a directory and mount gave me
the following warning:

	EXT2-fs warning: mounting unchecked fs, running e2fsck is recommended

On running e2fsck on the volume I got the following error:
	e2fsck 1.27 (8-Mar-2002)
	e2fsck: Bad magic number in super-block while trying to open
/dev/hdb2
	
	The superblock could not be read or does not describe a correct ext2
	filesystem.  If the device is valid and it really contains an ext2
	filesystem (and not swap or ufs or something else), then the
superblock
	is corrupt, and you might try running e2fsck with an alternate
superblock:
	    e2fsck -b 8193 <device>

Am I missing something in taking a backup of the snapshot volume. How else
can I accomplish the block/sector level backup of the snapshot volume?

Regards,
Manu.



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