US Patent 10409692 Garbage collection: timestamp entries and remove reference counts

One embodiment is related to a method for performing garbage collection at a backup system, comprising: determining an object that is present in a preceding backup but is no longer present in a present backup when or after the present backup is made; associating an indicator indicative of the preceding backup with the object in response to the determination that the object is no longer present in the present backup; determining whether the object is to be deleted from the backup system based on the indicator and a policy during garbage collection; and deleting the object in response to determining that the object is to be deleted.