This Question has 2 parts:
1) What snapshots can be safely removed, do I need to retain the ones from which a running instance was launched?
2) How are snapshots appearing from a shut down instance?
Forgive my ignorance, the manual(?) http://aws.amazon.com/ebs/faqs/ says "customers can create volumes based on any of their existing snapshots". I take it that means I only need 1 snapshot of a volume at any given time, and I do not need to keep snapshots from which running instances were launched? I know that's what it says but just want to be really careful here.
About a month ago, some logging filled the root partition of an EC2 instance. Afterwards it wasn't behaving and rather than fussing with it, I created a new instance from the most recent snapshot and shut down the original instance. Now I see weekly auto-snapshots appearing from both the new and old instance. It runs from the default user's crontab, but since the old instance is shut off, what's generating the snapshots? I checked the new instance and it has one line to run its own snapshot weekly.
I'm ready to delete the old instance and snapshots but having not done this before, I'm trying to read as much as I can before trashing something important...