Systems and Methods for Persistent Address Space Management

Abstract

Data is stored on a non-volatile storage media in a sequential, log-based format. The formatted data defines an ordered sequence of storage operations performed on the non-volatile storage media. A storage layer maintains volatile metadata, which may include a forward index associating logical identifiers with respective physical storage units on the non-volatile storage media. The volatile metadata may be reconstructed from the ordered sequence of storage operations. Persistent notes may be used to maintain consistency between the volatile metadata and the contents of the non-volatile storage media. Persistent notes may identify data that does not need to be retained on the non-volatile storage media and/or is no longer valid.

We claim: 
     
         1 . A method of operating a storage layer, comprising:
 receiving a message at the storage layer which specifies a logical identifier that is no longer in use by a storage client to reference data stored on a non-volatile storage medium;   storing, at the non-volatile storage medium, a persistent note configured to invalidate data stored at a storage location of the non-volatile storage medium that is assigned to the logical identifier;   receiving, from the storage client, a request comprising a first logical identifier; and   determining whether the first logical identifier corresponds to valid data stored on the non-volatile storage medium based on whether an entry corresponding to the first logical identifier exists in an index comprising entries corresponding to assignments between logical identifiers and physical storage locations of the non-volatile storage medium.