When I take a persistent disk snapshot, what are the consistency guarantees for this snapshot? I know it is not guaranteed to be "application consistent", but is it "crash consistent"? Or are there no consistency guarantees?
-- EDIT --
For comparison, Machine Images are guaranteed to be crash-consistent as is. However, the docs are silent on this issues with persistent disk snapshots.
TL;DR: PD disk snapshots are crash consistent.
From the Compute Engine Persistent documentation:
When you take a snapshot of a persistent disk, you don't need to take any additional steps to make your snapshot crash consistent. In particular, you do not need to pause your workload.