The standard way to delete things from cold storage is to encrypt each piece with keys that you can more easily to delete. You can also, of course, read in the

The standard way to delete things from cold storage is to encrypt each piece with keys that you can more easily to delete. You can also, of course, read in the data, rewrite it with the deleted portion removed, and write it out again. (Disclosure: I work at Google, though I don't know anything about how Google handles this)