Zone bit recording and Related Topics

Hard disk drive

2 links

Electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnetic material.

Internals of a 2.5-inch laptop hard disk drive

A disassembled and labeled 1997 HDD lying atop a mirror

Magnetic cross section & frequency modulation encoded binary data

Destroyed hard disk, glass platter visible

Diagram labeling the major components of a computer HDD

Recording of single magnetisations of bits on a 200 MB HDD-platter (recording made visible using CMOS-MagView).

Longitudinal recording (standard) & perpendicular recording diagram

An HDD with disks and motor hub removed, exposing copper-colored stator coils surrounding a bearing in the center of the spindle motor. The orange stripe along the side of the arm is a thin printed-circuit cable, the spindle bearing is in the center and the actuator is in the upper left.

Head stack with an actuator coil on the left and read/write heads on the right

Close-up of a single read-write head, showing the side facing the platter

Leading-edge hard disk drive areal densities from 1956 through 2009 compared to Moore's law. By 2016, progress had slowed significantly below the extrapolated density trend.

Two Seagate Barracuda drives, from 2003 and 2009 - respectively 160GB and 1TB. Seagate offers capacities up to 20TB.

8-, 5.25-, 3.5-, 2.5-, 1.8- and 1-inch HDDs, together with a ruler to show the size of platters and read-write heads

A newer 2.5-inch (63.5 mm) 6,495 MB HDD compared to an older 5.25-inch full-height 110 MB HDD

Inner view of a 1998 Seagate HDD that used the Parallel ATA interface

2.5-inch SATA drive on top of 3.5-inch SATA drive, showing close-up of (7-pin) data and (15-pin) power connectors

Close-up of an HDD head resting on a disk platter; its mirror reflection is visible on the platter surface. Unless the head is on a landing zone, the heads touching the platters while in operation can be catastrophic.

Diagram of HDD manufacturer consolidation

Early hard disk drives wrote data at some constant bits per second, resulting in all tracks having the same amount of data per track but modern drives (since the 1990s) use zone bit recording – increasing the write speed from inner to outer zone and thereby storing more data per track in the outer zones.

Group coded recording

2 links

In computer science, group coded recording or group code recording (GCR) refers to several distinct but related encoding methods for representing data on magnetic media.

This more efficient GCR scheme, combined with an approach at constant bit-density recording by gradually increasing the clock rate (zone constant angular velocity, ZCAV) and storing more physical sectors on the outer tracks than on the inner ones (zone bit recording, ZBR), enabled Commodore to fit 170 kB on a standard single-sided single-density 5.25-inch floppy, where Apple fit 140 kB (with 6-and-2 encoding) or 114 kB (with 5-and-3 encoding) and an FM-encoded floppy held only 88 kB.

Cylinder, head, and sector of a hard drive.

Cylinder-head-sector

1 links

Early method for giving addresses to each physical block of data on a hard disk drive.

As the geometry became more complicated (for example, with the introduction of zone bit recording) and drive sizes grew over time, the CHS addressing method became restrictive.

Disk sector

1 links

[[File:Disk-structure2.svg|thumb|upright=1.3|Figure 1: Disk structures:1. Track

This is known as zoned bit recording.

Sirius Systems Technology

1 links

Personal computer manufacturer in Scotts Valley, California.

One striking difference between it and other machines on the market at the time was the fact that the disc utilized a form of zoned constant linear velocity (ZCLV) (using 9 different speed-zones selected out of 15 supported by the hardware) with a variant of zone bit recording (ZBR) (11 to 19 sectors depending on zone) to spun at different speeds according to where the data was stored, running slower towards the outer edge of the disc in such a way that bit density (bits per cm passing the head), rather than rotational speed, was approximately constant.

Floppy disk

1 links

Obsolete type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined with a fabric that removes dust particles from the spinning disk.

8-inch, 5¼-inch (full height), and 3½-inch drives

A 3½-inch floppy disk removed from its housing

8-inch floppy disk,
inserted in drive,
(3½-inch floppy diskette,
in front, shown for scale)

3½-inch, high-density floppy diskettes with adhesive labels affixed

Imation USB floppy drive, model 01946: an external drive that accepts high-density disks

Front and rear of a retail 3½-inch and 5¼-inch floppy disk cleaning kit, as sold in Australia at retailer Big W, circa early 1990s

Different data storage media (Examples include: Flash drive, CD, Tape drive, and CompactFlash)

A floppy hardware emulator, same size as a 3½-inch drive, provides a USB interface to the user

Screenshot depicting a floppy disk as "save" icon

Disk notcher converts single-sided 5¼-inch diskettes to double-sided.

Rear side of a 3½-inch floppy disk in a transparent case, showing its internal parts

How the read-write head is applied on the floppy

Visualization of magnetic information on floppy disk (image recorded with CMOS-MagView)

A box of about 80 floppy disks together with one USB memory stick. The stick is capable of holding over 130 times as much data as the entire box of disks put together.

A more space-efficient technique would be to increase the number of sectors per track toward the outer edge of the disk, from 18 to 30 for instance, thereby keeping nearly constant the amount of physical disk space used for storing each sector; an example is zone bit recording.