It's too small. /56 should be the minimum unless there are hard technical reasons why you can't do that. My point was that a lot of ISPs seem to think that even

It's too small. /56 should be the minimum unless there are hard technical reasons why you can't do that. My point was that a lot of ISPs seem to think that even /63 is too big, and that's in a 128-bit address space. Surely they would be even more miserly than they currently are if you removed 99.9999..% of the address space? I was primarily thinking of residential ISPs; business ISPs tend to be a little bit better. That said, datacenters (or rather server/VPS providers) are absolutely terrible. Most of them give you no v6 allocation of your own at all. If you're lucky they let you use as many addresses as you like on your WAN segment, but good luck if you wanted to do a VPN or routed VM subnet.