When used in the same manner as external rotating drives (hard drives, optical drives, or floppy drives), i.e. in ignorance of their technology, USB drives' failure is more likely to be sudden: while rotating drives can fail instantaneously, they more frequently give some indication (noises, slowness) that they are about to fail, often with enough advance warning that data can be removed before total failure. USB drives give little or no advance warning of failure. Furthermore, when internal wear-leveling is applied to prolong life of the flash drive, once failure of even part of the memory occurs it can be difficult or impossible to use the remainder of the drive, which differs from magnetic media, where bad sectors can be marked permanently not to be used.[74]