taking lvm backup

[Tapas Mishra]

On Tue, Sep 28, 2010 at 2:27 PM, Alvin <info at alvin.be> wrote:
> One way to take a backup is to convert the LVM volumes to compressed qcow2
> images, like this:
> # qemu-img convert -c -f raw -O qcow2 /dev/nintendo/lvm1 /backup/lvm1.img
>
Hmm but I do not have that much space that if the LVM is 100Gb then
another 100 Gb of qemu image.
Or if the filesystem is not completely occupied it is possible to see
occupying less space.

Is there any other way?
Since the mount command as above suggested is asking me to specify the
filesystem type which I gave
as
mount -t lvm /dev/nintendo/lvm1 /mnt -o ro

gave following error
mount: unknown filesystem type 'lvm'

mount -t lvm2 /dev/nintendo/lvm1 /mnt -o ro

gave following error
mount: unknown filesystem type 'lvm2'

mount  /dev/nintendo/lvm1 /mnt -o ro
mount: you must specify the filesystem type

all the above three have given me errors.

There does exist a filesystem but out of 100 Gb only 15 Gb are
occupied in each case.
Also
It is a Dell Power Edge R710 server with 500Gb of hard disk.450Gb of
which is available.
and in this  I have used 400 Gb to created the above LVMs I mentioned.