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Track (disk Drive)
A disk drive track is a circular path on the surface of a disk or diskette on which information is magnetically recorded and from which recorded information is read. A track is a physical division of data in a disk drive, as used in the Cylinder-Head-Record (CCHHR) addressing mode of a CKD disk. The concept is concentric, through the physical platters, being a data circle per each cylinder of the whole disk drive. In other words, the number of tracks on a single surface in the drive exactly equals the number of cylinders of the drive. Tracks are subdivided into blocks (or sectors, pages) (see: Storage block and Virtual page). The term track is sometimes prefaced with the word logical (i.e. "3390-9 has 3 logical tracks per physical track") to emphasize that it is used as an abstract concept, not a track in the physical sense. See also * Hard disk drive * Disk sector In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CKD Disk
Count key data (CKD) is a direct-access storage device (DASD) data recording format introduced in 1964, by IBM with its IBM System/360 and still being emulated on IBM mainframes. It is a self-defining format with each data record represented by a Count Area that identifies the record and provides the number of bytes in an optional Key Area and an optional Data Area. This is in contrast to devices using Fixed-block architecture, fixed sector size or a separate format track. Count key data (CKD) also refers to the set of channel commands (collectively Channel Command Words, CCWs) that are generated by an IBM mainframe for execution by a DASD subsystem employing the CKD recording format. The initial set of CKD CCWs, introduced in 1964, was substantially enhanced and improved into the 1990s. CKD track format The reason for CKD track format is to allow data field lengths to vary, each recorded block of data on a DASD track, called a record has an associated count field which identifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hard Disk Platter
A hard disk drive platter or hard disk is the circular magnetic disk on which digital data is stored in a hard disk drive. The rigid nature of the platters is what gives them their name (as opposed to the flexible materials which are used to make floppy disks). Hard drives typically have several platters which are mounted on the same spindle. A platter can store information on both sides, typically requiring two recording heads per platter, one per surface. Design The magnetic surface of each platter is divided into small sub-micrometer-sized magnetic regions, each of which is used to represent a single binary unit of information. A typical magnetic region on a hard-disk platter (as of 2006) is about 200–250 nanometers wide (in the radial direction of the platter) and extends about 25–30 nanometers in the down-track direction (the circumferential direction on the platter), corresponding to about 100 billion bits per square inch of disk area (15.5 Gbit/cm2). The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Storage Block
In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc. For most disks, each sector stores a fixed amount of user-accessible data, traditionally 512 bytes for hard disk drives (HDDs), and 2048 bytes for CD-ROMs, DVD-ROMs and BD-ROMs. Newer HDDs and SSDs use 4096 byte (4 KiB) sectors, which are known as the Advanced Format (AF). The sector is the minimum storage unit of a hard drive. Most disk partitioning schemes are designed to have files occupy an integral number of sectors regardless of the file's actual size. Files that do not fill a whole sector will have the remainder of their last sector filled with zeroes. In practice, operating systems typically operate on blocks of data, which may span multiple sectors. Geometrically, the word sector means a portion of a disk between a center, two radii and a corresponding arc (see Figure 1, item B), which is shaped like a slice of a pie. Thus, the ''disk sector'' (Figure 1, it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Page
A page, memory page, or virtual page is a fixed-length contiguous block of virtual memory, described by a single entry in a page table. It is the smallest unit of data for memory management in an operating system that uses virtual memory. Similarly, a page frame is the smallest fixed-length contiguous block of physical memory into which memory pages are mapped by the operating system. A transfer of pages between main memory and an auxiliary store, such as a hard disk drive, is referred to as paging or swapping. Explanation Computer memory is divided into pages so that information can be found more quickly. The concept is named by analogy to the pages of a printed book. If a reader wanted to find, for example, the 5,000th word in the book, they could count from the first word. This would be time-consuming. It would be much faster if the reader had a listing of how many words are on each page. From this listing they could determine which page the 5,000th word appears on, and how ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hard Disk Drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating hard disk drive platter, platters coated with magnetic material. The platters are paired with disk read-and-write head, magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces. Data is accessed in a random-access manner, meaning that individual Block (data storage), blocks of data can be stored and retrieved in any order. HDDs are a type of non-volatile storage, retaining stored data when powered off. Modern HDDs are typically in the form of a small disk enclosure, rectangular box. Hard disk drives were introduced by IBM in 1956, and were the dominant secondary storage device for History of general-purpose CPUs, general-purpose computers beginning in the early 1960s. HDDs maintained this position into the modern er ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disk Sector
In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc. For most disks, each sector stores a fixed amount of user-accessible data, traditionally 512 bytes for hard disk drives (HDDs), and 2048 bytes for CD-ROMs, DVD-ROMs and BD-ROMs. Newer HDDs and SSDs use 4096 byte (4 KiB) sectors, which are known as the Advanced Format (AF). The sector is the minimum storage unit of a hard drive. Most disk partitioning schemes are designed to have files occupy an integral number of sectors regardless of the file's actual size. Files that do not fill a whole sector will have the remainder of their last sector filled with zeroes. In practice, operating systems typically operate on blocks of data, which may span multiple sectors. Geometrically, the word sector means a portion of a disk between a center, two radii and a corresponding arc (see Figure 1, item B), which is shaped like a slice of a pie. Thus, the ''disk sector'' (Figure 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cylinder (disk Drive)
Cylinder-head-sector (CHS) is an early method for giving addresses to each physical block of data on a hard disk drive. It is a 3D-coordinate system made out of a vertical coordinate ''head'', a horizontal (or radial) coordinate ''cylinder'', and an angular coordinate ''sector''. Head selects a circular surface: a platter in the disk (and one of its two sides). Cylinder is a cylindrical intersection through the stack of platters in a disk, centered around the disk's spindle. Combined, cylinder and head intersect to a circular line, or more precisely: a circular strip of physical data blocks called ''track''. Sector finally selects which data block in this track is to be addressed, as the track is subdivided into several equally-sized portions, each of which is an arc of (360/n) degrees, where n is the number of sectors in the track. CHS addresses were exposed, instead of simple linear addresses (going from ''0'' to the ''total block count on disk - 1''), because early hard drive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Storage Devices
Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processing unit (CPU) of a computer is what manipulates data by performing computations. In practice, almost all computers use a storage hierarchy, which puts fast but expensive and small storage options close to the CPU and slower but less expensive and larger options further away. Generally, the fast technologies are referred to as "memory", while slower persistent technologies are referred to as "storage". Even the first computer designs, Charles Babbage's Analytical Engine and Percy Ludgate's Analytical Machine, clearly distinguished between processing and memory (Babbage stored numbers as rotations of gears, while Ludgate stored numbers as displacements of rods in shuttles). This distinction was extended in the Von Neumann architecture, whe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
