Quick Notes First:
Formatting the new Disk
Suppose the Disk is /dev/sdb, the second scsi disk,
create as many partitions as you need using command n
Label them with command t as 8e for making it Linux LVM
Write and Exit with the command w.
Format the partitions you require using mkfs command
mkfs -t ext3 -c /dev/sdb1
vgextend VolGroup00 /dev/sdb1
lvextend -L 15G /dev/VolGroup00/LogVol01 ;for extending LogVol to 15GB
lvextend -L+1G /dev/VolGroup00/LogVol01 ;for adding one more GB to Logical Volume LogVol01
ext2online /dev/VolGroup00/LogVol01 ;for resizing the Logical Volumes
Thats it finished
On Ubuntu Intrepid 8.10 you need to use resize2fs to resize the lvm.