Digital Linear Tape (DLT)

Digital Linear Tape (DLT) is a backup tape storage technology developed by Digital Equipment Corporation (DEC) and purchased by Quantum Corp. who currently licenses the technology and trademark. Unlike other tape technologies DLT uses a 1/2 tape (as opposed to a 8mm tape)Which is about 60% wider then 8mm. This means you can store more data on half-inch tape then other smaller formats. DLTtape drives read and write data in a linear pattern on the tape. That is, each data track goes the entire length of the tape. When data is being recorded, the first set of tracks is recorded on the whole length of the tape. When the end of the tape is reached, the heads are repositioned to record a new set of tracks, and the tape is again recorded on its whole length,this time in the opposite direction. That process continues, back and forth, until the tape is full. Current DLTtape drives record either 128 tracks (DLT 4000 drives), 168 tracks (DLT1 drives), 208 tracks (DLT 7000 and DLT 8000 drives), or 448 tracks (SuperDLTtape drives) on half-inch tape. By comparison, helical scan systems record data in diagonal stripes across the tape. This diagonal pattern allows data tracks to be overlapped for very high data density. One of the drawbacks of such high density is the increasing difficulty it introduces in error detection and correction. Even a very small defect on a helical-scan tape will probably corrupt the data, because such a large amount of data is squeezed into a very small linear space.