Unless your LUN has LOTS of spindles underlying it, I would avoid carving it up into too many different separate sections just to "isolate" activity. The more "disks" you provision on a 4 disk RAID 5 (or 10) for example, the more head movement you will incur because they blocks for each disk are physically separated by a distance that require further head movement on the disks than you would have if you simply had ONE large drive that you dropped everything onto. This is a VERY COMMON mistake by DBAs/SAN admins.