Quantum DLT 2000 Handbook page 24

DLTtape drive recording
Figure 2-2 The DLTtape System's Linear Serpentine Recording
pattern writes data along tracks from one end of the DLTtape cartridge to
the other. Helical scan systems use read/write heads on a rotating drum to
record data in angled stripes across the tape.
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 (Super
DLTtape drives) on half-inch tape.
By contrast, helical scan systems record data in diagonal stripes
across the tape. This diagonal pattern allows data tracks to be over-
lapped for very high data density. One of the drawbacks of such
high density is the increasing difficulty it introduces in error detec-
tion 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. With DLTtape
Helical scan recording
QUANTUM DLTtape HANDBOOK 2.3