Device	Technology	Arrangement	Block arrangement	Sector Size	Error Correction	Speed
Hard Drive	Magnetic 8b10b-RLL Encoding NRZI Domain arrangement Logitudinal Side by side Latest technology Perpendicular Two-layer Material:	Parallel Tracks Both sides Multiple Platters Data arranged in sectors Sectors read sequentially Sectors addressed by c/h/s c - Cylinder h - Head s - Sector Only one head addressed at a time.	Inter-space Gap Binary-Data Error-check	512 bytes, 4096 - supported with EFI Unified Extensible Firmware Interface	ECC Low-density Parity	Constant rotationsl 3600 - Legacy and low-power external 7200 - Most consumer drives 10600 - Server, SCSI and SATA
CD-ROM - Audio	Optical Infra-red LED Laser 785 nm-wavelength 8to14 RLL encoding 1.6 micron between revolutons 0.8 micron pit.	Single Continuous Track 22,188 revolutions Track located on top side of disk. Viewed from bottom. User burnable CD-Rs have a wobble embedded in the recording track that provide centering and timing for rotaional speed control. The wobble in the track before the main data is also used as a copy protetion key.	44,100 samples/sec 16-bit sample x 2-channels 8-bit encoded on 14-bit Frame = 24-bytes audio + 4-bytes parity and one byte sub-code 33-byte frame Each frame separated by 27-bit sync word Sector = 98 frames Played at 75-frames/sec. Bytes in frame scrambled	2352 bytes per sector No separate Error-check block	Byte scrambling Parity Check at Frame level No error check at sector level	Constant linear speed 120 cm./sec. Speed varies from center to edge 530 RPM at hub to 200 RPM at rim.
CD-ROM - Data	Optical Infra-red LED Laser 785nm-wavelength 8 to 14 RLL encoding 1.6 micron between revolutons 0.8 micron pit.	Single continuous track 22,188 revolutions Track located on top side of disk. Viewed from bottom. User burnable CD-Rs have a wobble embedded in the recording -track that provide rotational timing for rotaional speed control. The wobble in the track before the main data is also used as a copy protetion key.	Uses 98 frames per sector and scrambling at frame level	Mode 1 Sector size Totals : 12 byte sync block 4 byte header 2048 bytes of data 288 byte ECC Mode 2 12 byte sync block 4 byte header 2336 bytes of data	Uses scrambling in frame Mode 1 uses frame parity check and ECC on sector Mode 2 uses only frame parity check.	Drive used as data drive capable of constant rational speeds of up to 48x Audio CD.
DVD	Optical Red-Orange LED Laser 650nm. 0.74 micron between revolutions 0.4 micron pits 7x increase in capacity 8to10 RLL encoding EFMPlus	Single continuous track Allows double sided disks or single-side dual layer. Double sided/dual layer possible but never commerically used. User burnable DVDs have a wobble embedded in the recording track that provide timing for rotaional speed control. The wobble in the track before the main data is also used as a copy protetion key.	8/16 RLL encoding EFMPlus modulation NRZI Sector : Header ID - type of info Sector number (LBA style) Other Data 2048 bytes - only one mode. Both 'data' and video treated as regular data. EDC Advanced form of ECC	Total sector count 2418 bytes. 2048 bytes data 4 byte EDC. Sync code between every 91 bytes.		Constant linear speed 1.4 MB/sec.
Blu-Ray	Optical Blue-violet LED Laser 405nm.	Single continuous track Theoretically capable of 8 layers Single layer - 27 GB Dual layer - 50 GB 4x layer - 100 GB All data treated as files. Uses UDF for filesystem. Movies - MPEG2 or MPEG4				Constant linear speed