Fakeback

Determines the best performance typical under read-only conditions. Since all backup systems must WRITE, backup performance will usually be lower than this number (consider at least 1/2). However, new advanced programs may use sophisticated multi-thread programming techniques or optimised drivers for IO and it is possible for these to equal, sometimes exceed FakeBack. Therefore, FakeBack is a good reference guide. If your backup program can do better than FakeBack, there’s probably not much you can do to improve performance.