You know you're having a bad day when your backup software requires 83 Terabytes of free space in order to proceed.
![This is real, not Photoshop Time Machine](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqgaMMRBpP6TYFkpdJoBmKxzeW62wWhvJOnKhUUvoWlHoUhHAEZDvuirKGGQEXV5e7lMus-x9nb6QYw-jS52f2R_kdrMAFXgXaYwLF0r3xk9QV7kpVw2zpZveKZw2B4D4LYYOK5RVfCkUv/s800/timemachine.png)
As it turns out, the filesystem on this disk needed repair. Disk Utility found an 82.95 terabyte file which appeared to be incorrect.