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A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to digital data. [ 1 ] [ 2 ] Blocks of data entering these systems get a short check value attached, based on the remainder of a polynomial division of their contents.
A cyclic redundancy check (CRC) is a non-secure hash function designed to detect accidental changes to digital data in computer networks. It is not suitable for detecting maliciously introduced errors.
On Windows NT operating systems, CHKDSK can also check the disk surface for bad sectors and mark them (in MS-DOS 6.x and Windows 9x, this is a task done by Microsoft ScanDisk). The Windows Server version of CHKDSK is RAID-aware and can fully recover data in bad sectors of a disk in a RAID-1 or RAID-5 array if other disks in the set are intact. [11]
A head crash, one type of disk failure. The platters should normally be smooth in modern drives, and a head crash results in partial to total data loss, as well as irreversible damage to the platters and heads. Particles may also be liberated during this process, making the insides of the drive not clean enough for operation.
Two kinds of redundancy are passive redundancy and active redundancy. Passive redundancy is used to achieve high availability by including enough excess capacity in the design to accommodate a performance decline. The simplest example is a boat with two separate engines driving two separate propellers.
Independent of checking the file system structure, modern file systems may offer a data scrubbing tool to check for silent corruption in stored data against a mirror or a checksum. Scrubs tend to be slow as they cover all data on a disk, but periodic runs can defend against data rot and help identify failing drives. [7]
[b] The file system could defragment the disk immediately after a deletion, but doing so would incur a severe performance penalty at unpredictable times. Now, a new file called F, which requires seven blocks of space, can be placed into the first seven blocks of the newly freed space formerly holding the file B, and the three blocks following ...
In engineering and systems theory, redundancy is the intentional duplication of critical components or functions of a system with the goal of increasing reliability of the system, usually in the form of a backup or fail-safe, or to improve actual system performance, such as in the case of GNSS receivers, or multi-threaded computer processing.