Resizing on demand without downtime up to a maximum of 64TB will allow running at that very high % of provisioned capacity.

I did a fair number of tests last year and couldn't get anything like that. If anyone is interested, the poorly formatted output of that is here:

https://github.com/halbritt/benchmarks

Can you please elaborate a little? EFS scales with size, i.e. did you have at least a few hundred GB on there or was it mostly empty? Roughly how many IOPS did you get?

IIRC, I populated the thing with 10TB or thereabouts.

For small block sizes, I got hundreds of IOPS.

Latency was pretty terrible in almost all cases.

I wrote a great deal on this topic for internal consumption. Those benchmarks weren't really meant for the general public. My biggest conclusion is that EFS isn't useful for any workload where performance is a concern. Unfortunately, it's priced so high, that I'd never consider using it otherwise.

You can always dynamically resize at the rate of 1GB.

That's still a drawback as your app needs to manage dynamic resizing. While aws may not be more expensive, it's more convenient