Shoe-shining or backhitching – a term used in backup context – is a repeated back-and-forth-motion a tape device makes when the data flow is interrupted or is too slow. The process itself is destructive for the tape device, as well as for the tape cartridge.
A tape cartridge is a sequential medium requiring a continuous flow of data to keep the internal band in motion. When the data stream gets interrupted or the backup server is sending data slower than the tape drive processor, the tape device is obligated to stop. The stop causes an offset of the writer and when resuming the device is required to position the writer back to the spot containing the blocks of the last write operation. The process: stop (end-of-data-stream), reposition (finding the right spot again), write (continue data stream) and repeat is what is called shoe-shining.