zfs rebalance

[dvaezazizi]

I'm sure this topic has been brought up before, but is there any plan to add the ability to rebalance data after adding vdevs? The performance hit is large and is a pain to deal with at the enterprise level.

[rincebrain]

As much as it'd be nice to have, tThe performance hit of doing this, engineering time aside, would be pretty horrific, no matter how you slice it - you'd end up with giant indirection tables like with vdev evacuation on a nontrivial vdev, and all the weird performance implications that ensue there.

I can't say that nobody will ever invent a solution to that that doesn't have gross performance implications, but I think it would involve significantly redesigning the constraints ZFS operates under.