1. A method to allocate a block of persistent storage, the method comprising: forming a storage service string to include metadata, the metadata to indicate one or more characteristics for a storage service associated with the block of persistent storage, the storage service string being used to allocate the block of persistent storage, wherein the one or more characteristics for the storage service comprises: a size for the block of persistent storage; an expiration time period for the block of persistent storage; a number of allowed reads per given time period for the block of persistent storage; or a number of allowed writes per given time period for the block of persistent storage.