[hamandcheese]

I assume the host moves, not the disks. My next assumption is that the host moving would involve downtime for the host, so no need to bother simulating some hotplugs.

(I know that live migrations are at least in theory possible, but I don’t know why GCP would go through all the effort)

(I’m also making a lot of assumptions about things I am not an expert in)

[paulfurtado]

The disks are physically attached to the host. The VM running on that host moves from one host to another. GCP live-migrates every single VM running on GCP roughly once per week, so live migration is definitely seamless. Standard OSS hypervisors support live migration.

When hardware fails, the instance is migrated to another machine and behaves like the power cord was ripped out. It's possible they go down this path for failed disks too, but it's feasible that it is implemented as the disk magically starting to work again but being empty.

You can read more about GCP live migrations here: https://cloud.google.com/compute/docs/instances/live-migrati...