Device Capacity Track
Structur8		 Sector
Size		 Recording
Mechanism		 Disc and Data
Speed
Magnetic
Hard Drive		 10MB ot Multi-TB

500MB or 750MB per platter,
1-2 platters most common

 Many separate concentric parallel tracks.

Track on both
sides of platter.

Tracks divided into sectors.

Number of sectors per track can vary(zoned)

Older 512 Bytes data.

Newer 4KiB data - (needs UEFI support at bios and OS levels)

Other sizes possible, but not common.

 Magnetic recording
Original : Iron oxide

Newer : stacked Crome-cobalt.

 Constant rotational speed

3600 RPM. Legacy and small external drives.

7200 RPM. Modern Drives.

10000, 15000 RPM Server grade SCSI drives.

Compact Disc 650 MB or
74 minutes of audio
Capacities - 700,800,900 MB
available but determined by physical design.		 Single continuous physical data track.

Recordable disc contain a second "wobble" track for timing.

Sectors arranged sequentially from center out

Data Sector size 2352 bytes
Header : 16 bytes
Data : 2048 bytes
ECC : 288 bytes

Music Sector size 2352 bytes
Data : 2352 bytes
Sector id and some error correction
embedded in sector.

Detection of reflective(lands) and non-reflective(pits) surface.

Infra-red led laser 780nm

Data is embedded in NRZI signal
using 8-to-14 (EFM) RLL encoding with a 3 bit separator.

1s represented by change in
reflectivity.

Music : constant linear speed. (Speed track moves under read head).
500 rpm to 200 rpm, inner to outer edge.
~1.2 m/s, Target : 150 KiB/s transfer rate.

Data drives : constant rotational speed.
Up to 52x legacy speed or ~ 10,000 rpm. Target : 7.6 MiB/s

DVD
Ditital Versatile Disc		 Data : 4.7 GB (single side, single layer)
About 130 minutes of video

Data : 8.5 GB (single side, double layer)

Data : 9.4 GB (double side, single layer)

Data : 17.08 GB (double side, double layer)

 Single continuous physical data track

Recordable disc contain a second "wobble" track for timing.

Sectors arranged sequentially from center out.

Sector size : 2366 bytes
Sector ID : 4 bytes
ID errror Detection : 2 bytes
Data : 2048i bytes
Error Detection code : 4bytes
Sector contents is interleaved and an additiona 302 bytes of RS-ECC code added.

DVD makes no distinction between Audio, video, or data at the sector level.

Detection of reflective(lands) and non-reflective(pits) surface.

Red-orange led laser 650 nm

Data is embedded in NRZI signal using 8-to-16 encoding and (2,10) RLL but eliminate the need for separator bits.

1s represented by change in reflectivity.

Rotational speed for movies : 1530 rpm (inner) to 630 rpm (outer edge).
Speed faster, and possibly constant, for data transfers.

Video transfer target : 1:32 MiB/s

Data transfer target : up to 16x video.

Blu-Ray Single layer : 25 GB

Dual layer : 50GB

3 and 4 layer possible (100GB/128GB)

Single physical data track

Writable discs use second track for timing and alignment.

 64KB with ECC

Video uses MPEG-2 (standard) or MPEG-4/HD.263 high-def.

 Blue-violet diode laser 405 nm.

17pp encoding - 17 parity preserve-prohibit repeated minimun run-length transistion.

17 bit run length, works better with smaller bits and multi-layer aspect of Blu-ray.

Transfer target : 4.5 MiB/s