EC2 Instance Block Device Mappings

[krjackso]

AWS does some weird things aroundblock device mappings including:

• mapping ephemeral volumes from the gold ami even if the instance can't have that many in the ruby sdk
• unmapping ephemeral volumes from the gold ami that the instance can't have
• not telling you how many volumes each type should have, anywhere

So Cumulus needs to be able to handle knowing how many ephemeral volumes to have in the mapping for a launching instance. We should also do a better job at mounting ebs volumes in available slots.