A request to access to a logical location in a file stored in a content addressable storage (CAS) system can be processed by retrieving first tree data from a first node in a first hash tree that represents a first version of the file. Based on the first tree data, a second node is selected from which a CAS signature is compared to a reserved CAS signature to determine the proper file version. In response to a match, a third node is accessed in a second hash tree that represents a second version of the file. Tree data is retrieved from a third node.