ZFS expansion-a-pollooza

[Stux]

@iamwoz

and am seeing the ALLOC / FREE and CAP changing slowly but no change to this:

RaidZ Expansion Space Reporting is wonky.

RaidZ Expansion on ElectricEel Nightlies

@etorix is right. Raidz Expansion space accounting is incorrect. There is more free space available than indicated and it’s not just because existing data is stored with the old parity ratio. Rebalancing will not correct. This is the explanation