But, since block tiering is done inside the storage operating system as a proprietary solution, it has several limitations when it comes to efficiency of reuse and efficiency of storage savings. Firstly, with block tiering, the proprietary storage filesystem must be involved in all data access since it retains the metadata and has the “map” to putting the file together from the various blocks. This also means that the cold blocks that are moved to a lower tier or the cloud cannot be directly accessed from the new location without involving the proprietary filesystem because the cloud does not have the metadata map and the other data blocks and the file context and attributes to put the file together. So, block tiering is a proprietary approach that often results in unnecessary rehydration of the data and treats the cloud as a cheap storage locker rather than as a powerful way to use data when needed.