We currently have an ext3 partition running on LVM which is using all of the 20G disk allocation (doh!) so we are unable to create any snapshots due to:
"Insufficient Free Extents Available"
We want to reduce the partition size to 15G so we have 5G to play with for snapshots and other LVM goodness.
First we umount our directory if it is currently in use:
We then run a fsck on our device
e2fsck -f /dev/path/to/lvm/
We then resize the ext3 partition "before" we resize the LVM partition
resize2fs -p /dev/path/to/lvm/ 15G
Then we resize the the LVM parition using the imaginatively named lvresize
lvresize /dev/path/to/lvm/ --size 15G
And we're done. Yay!