I'm trying to implement volume thin-provisioning. Volume size is 2TB, free space in the aggregate is 1TB. The only way to set volume space guarantee to 'none' is to set fractional reserve to 100% (Data ONTAP 7.3.2 limitation). As I see it, 100% of space is reserved when I set 100% fractional reserve and then reclaimed back to the aggregate when I set space guarantee to none. And we're OK with it. But the silly thing is that I can't set fractional reserve to 100%, because I don't have enough free space in the aggregate (only 1 TB, when 2TB is needed):
> vol options vmfs_volume1 guarantee none
vol options: Volume option guarantee can be modified only if the fractional_reserve is 100
> vol options vmfs_volume1 fractional_reserve 100
vol options: There is not enough available space in the volume to increase the fractional_reserve.
I love it. Answering my question myself again. Data ONTAP tried to reserve 100% fractional reserve because there were other LUNs in the volume which I forgot to make thin provisioned. After I thin provisioned all LUNs, I was able to set fractional reserve to 100% without reserving any space in the volume. Then I set space guarantee to none without any problem.