Here are the commands to reduce an ext3 file system and also the Logical Volume that holds it.
Warning please make sure you leave enough space for the files inside, or data may be lost.
First make sure the files system isn’t mounted then.
e2fsck -f /dev/VolGroup00/disk1_rootimg
resize2fs -p /dev/VolGroup00/disk1_rootimg 15G
lvreduce –size 15G /dev/VolGroup00/disk1_rootimg
This should reduce the file system to 15G