Doing snapshots with XFS filesystems
There are several Howtos on the net, which tell you to do the following if you want to create LVM snapshots if you have XFS filesystems on your logical volumes:
xfs_freeze -f /mnt/xfs lvcreate -L 10G -s -n fs_snap /dev/VolGroup00/LogVol01
If you try that on a system without LVM2, the following will happen: lvcreate will hang until you do an
xfs_freeze -u /mnt/xfs
in a second terminal. After that lvcreate will create the snapshot for you.
If you use LVM2 (like CentOS 4 or CentOS 5 do), lvcreate will do the freezing for you.
lvcreate -L 10G -s -n fs_snap /dev/VolGroup00/LogVol01
will freeze your xfs filesystem before creating the snapshot.