What is the behavior of the block volume when an instance is stopped, deleted or crashed?
A block volume is persistent which means that it can live without being attached to an instance. Nevertheless, when an Instance is deleted, the following can be expected:
When the instance is deleted via the Scaleway console, you will be asked if you want the distant block volumes to be deleted as well or not.
When deleting an instance via the API, all the attached volumes (local and block storage) are deleted. So, if you want to keep your local volumes, you must use the archive action instead of terminate. And if you want to keep block-storage volumes, you must detach them beforehand you issue the terminate call.