US Patent 10437474 Overwriting compressed data extents

A technique for overwriting compressed data tests whether new data compressed with a first compression procedure fits within spaces provided for previous data. If the compressed new data does not fit, the technique compresses the new data using a second compression procedure. Assuming the second compression procedure reduces the compressed size of the new data to fit the available space, the technique stores the new data in the same location as the previous data. In this manner, overwrites can be accommodated in place without the need to create new mapping metadata.