Too late to edit, so I'll put that up here: we do migrate your local SSD but it's best effort and it takes a while (something like 30 minutes maybe?). But for c

Too late to edit, so I'll put that up here: we do migrate your local SSD but it's best effort and it takes a while (something like 30 minutes maybe?). But for comparison, our SSDs have crazy amounts of read/write bandwidth (1 gigabyte per second) compared to a single spinning disk. And while your VM is still going, it's not that disruptive to be re-syncing an SSD, randomly seeking around a hard drive while someone is trying to use it for say streaming reads will take their reasonable performance and tank it. tl;dr: Yes, we do this for our scratch disk SSDs, but you wouldn't want to rely on this for a guaranteed durable storage (as it'll take a really really long time to move 100 GiB of HDD).