Hi,
An alternative is also just thin provisioning your LUNs. If you don't space reserve your LUN's and have no guarantees on your volumes, then you don't really use any extra space just making the volumes 10-20% larger than your luns. In the end, it can really make life easier because you really only have to watch the aggregate filling levels. The added value is, of course, that you can use the blocks that have been ordered and "reserved" with full provisioning for other things.
Just a thought. It made my life a lot easier.