[citation needed] [3] DVD-R DL has compatibility issues with legacy DVD-ROM drives known as pickup head overrun.
One of the techniques employed to help compensate for these reliability shortcomings is a 10% increase in minimum mark (digital 0 or 1) length on the disc, with a corresponding 10% increase in rotation speed and 10% reduction in gross recordable capacity, accounting for the lower capacity of a single-sided dual-layer DVD at 8.5 billion bytes, versus a double-sized, single-layer DVD at 9.4 billion (for 12 cm discs).
Detail differences in formatting and file structure mean the "usable" data area capacity does not change by exactly this much, but for all intents a DVD-R DL has effectively 20/11ths the capacity of a DVD-R SL, and the same holds for +R, commercially pressed, and 8 cm discs.
[5] Many current DVD recorders support dual-layer technology, and the price is now comparable to that of single-layer drives, though the blank media remains more expensive.
For comparison, the table below shows storage capacities of the four most common DVD recordable media, excluding DVD-RAM.
(SL) stands for standard single-layer discs, while DL denotes the dual-layer variants.