1. A method for backing-up a computing system, comprising: storing a history of a filesystem directory in a set of fields of a global history table associated with the filesystem directory, wherein a field in the set of fields includes a reference identifier associating the filesystem directory with a computing system backup; generating a local history table of filesystem objects that have changed since storing a first backup of the computing system, the local history table including attributes of the filesystem objects and a set of operations associated with changes to the filesystem objects; transferring, from the computing system to a backup server, a second backup of the computing system, the second backup including a block level representation of at least a portion of a data storage medium associated with the computing system including the changed filesystem objects; merging the local history table with the global history table stored on the backup server, the global history table mapping a history of filesystem objects to a set of block level backups of the computing system including the first backup of the computing system and the second backup of the computing system, wherein the merging comprises updating, for each filesystem object included in the local history table, a set of fields of the global history table associated with the each filesystem object according to at least one operation of the set of operations, the at least one operation selected from at least one of an object create operation, an object delete operation, an object move operation, and an object rename operation, and wherein a filesystem object included in the local history table is a filesystem file and the merging comprises updating a set of fields of the global history table associated with the filesystem file according to a filesystem object change operation; determining that a third backup has expired; identifying fields of the global history table associated with the third backup; deleting the identified fields from the global history table; identifying, in response to the deleting, filesystem objects in the global history table that do not have fields associating the filesystem object state with a backup; and removing the identified file system objects from the global history table.