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Fwd: [dm-devel] cow snapshot on cloop device





---------- Forwarded message ----------
From: Jacob Broido <jacob broido gmail com>
Date: Aug 24, 2005 7:00 PM
Subject: Re: [dm-devel] cow snapshot on cloop device
To: Kevin Corry <kevcorry us ibm com>

I am using dmsetup directly. and I do the following:
1) Create an empty file that will be used as cow backing storage
2) losetup the backing file to /dev/loop0
3) create a snapshot of main root_device on /dev/loop0
4) mount the cow snapshot


Here is the info you requested:
The kernel is a - 2.6.11.10 + xen patch.
=======================================================
/ # dmsetup ls
root_master         (253, 0)
root_cow0        (253, 1)
/ # dmsetup table
root_master: 0 4096128 linear 240:0 0
root_cow0: 0 4096128 snapshot 253:0 7:0 P 8

/ # cat /proc/partitions

major minor  #blocks    name

7    0        loop0
8    0        sda
8    1        sda1
8    2        sda2
8    3        sda3
240    0        cloop0
252    0        dm-0
253    1        dm-1

/ # cat /proc/mounts
rootfs / rootfs rw 0 0
/dev/root.old  / ext2 rw 0 0
/proc /proc proc rw,noadirtime 0 0
/sys  /sys sysfs rw 0 0
/dev/hdc /cdrom iso9660 ro 0 0
/ramdisk /ramdisk tmpfs rw 0 0
/dev/mapper/root_cow0 /cow ext2 rw.noatime 0 0
====================================================


On 8/24/05, Kevin Corry < kevcorry us ibm com> wrote:
On Wed August 24 2005 11:35 am, Jacob Broido wrote:
> Hi,
> I am trying to set a cow snapshot on a cloop device.
> I managed to create a snapshot and mount it as read/write, but it appears
> that the data inside the /cloop appears invalid:
>
> Binary executables appear to be invalid, I perfomed diff between files on
> snapshotted /dev/cloop, and the same files accessed directly through cloop.
>
> The files were diffrent,
> anyone has idea as to what can be the reason for this?

Are you using LVM, EVMS, or dmsetup to create your snapshot? Please send in
the output from "dmsetup ls" and "dmsetup table", as well as the contents
of /proc/partitions and /proc/mounts, after you have activated and mounted
your snapshot.

--
Kevin Corry
kevcorry us ibm com
http://www.ibm.com/linux/
http://evms.sourceforge.net/



--
Not gonna be king of the world if you're slave to the grind
- Skid Row


--
Not gonna be king of the world if you're slave to the grind
- Skid Row
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