What are two methods of protecting LUN overwrites using Snapshot copies on a volume with...

https://communities.netapp.com/groups/chris-kranz-hardware-pro/blog/2009/03/05/fractional-reservation--lunoverwrite

From the article:

"If you reduce the Fractional Reservation to 0, you need to make sure the rate of change is within the volume size, or you need to make sure the volume can auto-grow when required or even snap auto-delete to reduce the reserved blocks and free up space (although I am not a huge fan of snap auto-delete for various reasons)."