Comment 1 for bug 2020028

This is the expected behavior.

evacuate of image-backed vms rebuilds the root disk because that is the expected behaviour in a cloud env where the instance root disk should not contain any valuable data.

This is functioning precisely how the API was designed to work.

in fact, the preservation fo disk for BFV or instance with shared storage is perhaps the more surprising aspect.

evacuate should be assumed to be destructive unless you are using boot form volume.

it may or may not be destructive depending on the storage configuration of the compute ndoes when used with non boot from volume instnaces.