RaidZ Expansion on ElectricEel Nightlies


Support for RaidZ Vdev Expansion is now available in ElectricEel Nightlies.
For those who do not know its a new feature that allows to extend an existing raidz vdev with another disk, e.g. from a 5 wide raidz to a 6 wide raidz.

Extend button is available when clicking in the top level raidz vdev on the pool status page.

As you can see, the caveat of this operation is that the parity ratio is maintained.
That essentially means the usable capacity will be lower when compared to creating a fresh vdev with that same number of disks.
To fix that one would have to essentially rewrite all the data to use the new parity ratio to get to full capacity.

As always, we do not recommend any production data to be used in Nightlies but we welcome the community of early testers to help us verify this functionality is working appropriately and squash any remaining bugs, either in the UI/API or at the ZFS level.


I was under the impression that only “pre-existing data on the expanded vdev” would use the “pre-expanded parity ratio”, is that not correct?

That’s correct.

I’d suggest inserting the words “pre-existing data on” after “The” and before “expanded vdev” in the caveat :slight_smile:

I read the original caveat as saying the vdev would use the pre-expanded ratio for future data too.

Is an expanded pool compatible with DragonFish at this stage?

You should not be able to import an ElectricEel pool into Dragonfish.