[linux-lvm] LVM snapshot - "dd" file size

[Thomas Bellembois <thomas bellembois gmail com>]

Hi!

I am using LVM partitions on a Debian Xen system.
I use LVM snapshots to clone and backup my virtual machines.

I have noticed that the ISO file created with the "dd" command it much
bigger that the partition used space (actually 4.7GB for the ISO - 500MB
used space). No problem if I mount the LVM snapshot and "tar" all of the
data.

I have googled the question and read that "dd" also copy "not used space".
Why is the ISO file so big ? Is the "tar" method less safe ?
Is there a better solution ?

Thanks for your answers.

Regards,

Thomas