in the case of file systems, 'improving' around the original design decisions is often impossible. take hfs+ for example: almost all the filesystem metadata is stored in a single b-tree called the catalog. doing almost anything with an hfs+ volume requires exclusive access to the catalog, which locks out all other callers for the duration of the file operation. the solution is to spread the metadata out to other parts of the disk, but that can't be done without breaking hfs+ compatibility.