US Patent 10140307 Efficiently managing reference weights for write splits

A technique for performing overwrites on shared data blocks in a file system transfers reference weights of block pointers to other block pointers that share those data blocks. To overwrite a portion of a file stored in a shared data block pointed to by a first block pointer, a file system manager locates a second block pointer in the file system that points to the same data block. The first block pointer has a first reference weight, and the second block pointer has a second reference weight. The file system manager transfers the first reference weight to the second block pointer, e.g., by replacing the second reference weight with the sum of the first reference weight and the second reference weight.