A method includes receives data representing a changed chunk of data in a current revision of a data volume, the changed chunk includes data having changes from previous data of a previous revision of the data volume. The method creates a block of data representing the changed chunk of data on the object store, the object store also stores previous revision data of the previous revision. The method determines a previous index stored on the object store corresponding to the previous revision, which includes entries including at least one corresponding to the previous revision data. The method creates a revised index that updates the corresponding entry with updated entry data representing the changed chunk of data. The method includes deleting, from the object store, each particular block of data stored on the object store that is no longer associated with an entry on any index stored on the object store.