In computing (specifically data transmission and data storage), block size indicates a nominal size, usually expressed in bytes or bits, of a block of data. Data thus structured is said to be blocked. The process of putting data into blocks is called blocking. Blocking is used to facilitate the handling of the data-stream by the computer program receiving the data. Blocked data is normally read a block at a time. Blocking is almost universally employed when storing data to 9-track magnetic tape, to rotating media such as floppy disks, hard disks, and optical discs, and to NAND flash memory. Memory (Random Access Memory) Look up computing in Wiktionary, the free dictionary. ... This article or section does not cite any references or sources. ... In computer science a byte is a unit of measurement of information storage, most often consisting of eight bits. ... This article is about the unit of information. ... Compact audio cassette Magnetic tape is a non-volatile storage medium consisting of a magnetic coating on a thin plastic strip. ... A floppy disk is a data storage device that is composed of a disk of thin, flexible (floppy) magnetic storage medium encased in a square or rectangular plastic shell. ... Typical hard drives of the mid-1990s. ... The optical lens of a compact disc drive. ... A USB flash drive. ...

Most file systems are based on a block device, which is a level of abstraction for the hardware responsible for storing and retrieving specified blocks of data, though the block size in file systems block may be multiple of the physical block size. In classical file systems, a single block may only contain a part of a single file. This leads to space inefficiency due to internal fragmentation, since file lengths are often not multiples of block size, and thus the last block of files will remain half-empty. This will create slack space. Some newer file systems attempt to solve this through techniques called block suballocation and tail merging. In computing, a file system (often also written as filesystem) is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. ... abstraction in general. ... For other uses, see Hardware (disambiguation). ... A computer file is a collection of information that is stored in a computer system and can be identified by its full path name. ... In a computer operating system, fragmentation is a consequence of allocating and freeing differently-sized blocks of data storage. ... Slack space or file slack is the area between the end of a file and the end of the last cluster or sector used by that file. ... It has been suggested that Tail packing be merged into this article or section. ... It has been suggested that this article or section be merged into Block suballocation. ...

Block storage is normally abstracted by a file system or database management system for use by applications and end users. The physical or logical volumes accessed via Block I/O may be devices internal to a server, direct attached via SCSI or Fibre Channel, or distant devices accessed via a storage area network (SAN) using a protocol such as iSCSI, or AoE. Database management systems often use their own Block I/O for improved performance and recoverability as compared to layering the DBMS on top of a file system. In computing, a file system (often also written as filesystem) is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. ... This article or section does not cite any references or sources. ... This article or section does not adequately cite its references or sources. ... In computing, a storage area network (SAN) is an architecture to attach remote computer storage devices such as disk array controllers, tape libraries and CD arrays to servers in such a way that to the operating system the devices appear as locally attached devices. ... . The initial letter is shown capitalized due to technical restrictions. ... ATA over Ethernet (AoE) is a network protocol developed by Coraid, Inc. ...

See also

• block allocation map
• block size (cryptography)
• Disk sector

Here, the View BAM utility on the Commodore 1541 Test/Demo Disk is displaying a portion of the block allocation map for that disk. ... In modern cryptography, symmetric key ciphers are generally divided into stream ciphers and block ciphers. ... In the context of computer hardware, a sector is a sub-division of a track on a magnetic disk or optical disc. ...

External links

• PHWiki:Block device