=====Overview=====
Snapshots are VERY versatile solution for backup strategy and often THE ONLY solution for a very big databases. The ability to backup terabytes worth of data in couple seconds is indeed a big plus. Other big plus is that it works with almost all storage engines: MyISAM, InnoDB, BDB and others. You still need to log the tables with read lock anyway, so it isn't Hot hot backup, but since it is very fast it is close to it.
In nutshell performing a hot backup is consist of the following:

  * Lock all tables with Read lock
  * Perform Snapshot and store it to a device
  * Periodically copy the device

=====Backup=====
It is very important to have LVM installed and configured on your file system.