I'm aware, but it's not BP rewrite. It's a workaround for not having BP rewrite. It's a fine workaround for not having BP rewrite. Enough such workarounds ca

I'm aware, but it's not BP rewrite. It's a workaround for not having BP rewrite. It's a fine workaround for not having BP rewrite. Enough such workarounds can make BP rewrite unnecessary -- that is what was expressed in that talk, but it's not that vdev evac == BP rewrite or that vdev evac == a bit of BP rewrite. BP rewrite is still needed for defragmentation, and for other reasons too (like if you wanted to change the configuration of a zpool to have more mirrors or stripes, or if you wanted to change compression algorithms, etc). (A proper CAS would not be able to handle things like compression algorithms, unfortunately, not unless the filesystem hashed the decompressed block rather than the compressed block, but that has security issues if you don't trust the storage, so it's not ideal. Of course, if you don't trust the storage then you need to be signing/MACing Merkle hash tree roots, but that's another story.)