Zone bit recording

In computer storage, zone bit recording (ZBR) is a method used by disk drives to optimise the tracks for increased data capacity.

Storing more bits per track equates to achieving a higher total data capacity on the same disk area.

Since both hard disks and floppy disks typically number their tracks beginning at the outer edge and continuing inward, and because operating systems usually fill the lowest-numbered tracks first, this is where the operating system normally stores its own files during its initial installation onto an empty drive.

Testing disk drives when they are new or empty after defragmenting them with some benchmarking applications will often show their highest performance.

After some time, when more data is stored in the inner tracks, the average data transfer rate will drop, because the transfer rate in the inner zones is slower; this, combined with the head's longer stroke and possible fragmentation, may give the impression of the disk drive slowing down over time.

Physical layout of sectors in a zone-bit disc: As distance from the centre increases, the number of sectors in a given angle increases from one (red) to two (green) to four (grey).