Surely they'll use a similar allocation strategy to what ZFS currently uses to allocate disk sectors. And of course if you mix a 4TB and a 8TB drive in a AnyRaid-Mirror configuration, you can only ever have 4TB redundant, so like current ZFS I assume you'll see 4TB. But if you then add a 12TB drive later, you can get 12TB mirrored.

> Is it going to be accepted upstream?

Good question. The S3 storage backend was initially said to be upstreamed, but ended up staying private to maintain a competitive edge.

Haven't checked out HexOS before, but given they're partnering with TrueNAS[1] and hiring Klara, Inc for development, one can certainly hope so.

[1]: https://www.truenas.com/blog/powered-by-truenas-hexos/