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Disk Buffer
In computer storage, a disk buffer (often ambiguously called a disk cache or a cache buffer) is the embedded memory in a hard disk drive (HDD) or solid-state drive (SSD) acting as a buffer (computer science), buffer between the rest of the computer and the physical hard disk platter or flash memory that is used for storage. Modern hard disk drives come with 8 to 256 Mebibyte, MiB of such memory, and solid-state drives come with up to 4 GB of cache memory. Since the late 1980s, nearly all disks sold have embedded microcontrollers and either an Advanced Technology Attachment, ATA, Serial ATA, SCSI, or Fibre Channel interface. The drive circuitry usually has a small amount of memory, used to store the data going to and coming from the disk platters. The disk buffer is physically distinct from and is used differently from the page cache typically kept by the operating system in the computer's main memory. The disk buffer is controlled by the microcontroller in the hard d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disk Array Controller
A disk array controller is a device that manages the physical disk drives and presents them to the computer as logical units. It often implements hardware RAID, thus it is sometimes referred to as RAID controller. It also often provides additional disk cache. ''Disk array controller'' is often ambiguously shortened to ''disk controller'' which can also refer to the circuitry responsible for managing internal disk drive operations. Front-end and back-end side A disk array controller provides front-end interfaces and back-end interfaces. * The back-end interface communicates with the controlled disks. Hence, its protocol is usually ATA (a.k.a. PATA), SATA, SCSI, FC or SAS. * The front-end interface communicates with a computer's host adapter (HBA, Host Bus Adapter) and uses: ** one of ATA, SATA, SCSI, FC; these are popular protocols used by disks, so by using one of them a controller may transparently emulate a disk for a computer. ** somewhat less popular dedicated protoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SATA
SATA (Serial AT Attachment) is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PATA) standard to become the predominant interface for storage devices. Serial ATA industry compatibility specifications originate from the Serial ATA International Organization (SATA-IO) which are then released by the INCITS Technical Committee T13, AT Attachment (INCITS T13). History SATA was announced in 2000 in order to provide several advantages over the earlier PATA interface such as reduced cable size and cost (seven conductors instead of 40 or 80), native hot swapping, faster data transfer through higher signaling rates, and more efficient transfer through an (optional) I/O queuing protocol. Revision 1.0 of the specification was released in January 2003. Serial ATA industry compatibility specifications originate from the Serial ATA Inte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journaling Block Device
JBD, or journaling block device, is a generic block device journaling layer in the Linux kernel written by Stephen Tweedie from Red Hat. JBD is filesystem-independent. ext3, ext4 ext4 (fourth extended filesystem) is a journaling file system for Linux, developed as the successor to ext3. ext4 was initially a series of backward-compatible extensions to ext3, many of them originally developed by Cluster File Systems for ... and OCFS2 are known to use JBD. JBD exists in two versions, JBD and JBD2. JBD was created with ext3 in 1998. JBD2 was forked from JBD in 2006 with ext4, with the goal of supporting a 64-bit (as opposed to 32-bit-only in JBD) block number. As a result, the maximum volume size in ext4 is increased to 1 EiB compared to 16 TiB in ext3 (assuming 4 KiB blocks). JBD2 is backward-compatible. OCFS2 starting from Linux 2.6.28 uses JBD2. The old JBD was removed with the dedicated ext3 driver in Linux 4.3 (2015). JBD structures Atomic handle An atomic handle is ba ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ext4
ext4 (fourth extended filesystem) is a journaling file system for Linux, developed as the successor to ext3. ext4 was initially a series of backward-compatible extensions to ext3, many of them originally developed by Cluster File Systems for the Lustre file system between 2003 and 2006, meant to extend storage limits and add other performance improvements. However, other Linux kernel developers opposed accepting extensions to ext3 for stability reasons, and proposed to fork the source code of ext3, rename it as ext4, and perform all the development there, without affecting existing ext3 users. This proposal was accepted, and on 28 June 2006, Theodore Ts'o, the ext3 maintainer, announced the new plan of development for ext4. A preliminary development version of ext4 was included in version 2.6.19 of the Linux kernel. On 11 October 2008, the patches that mark ext4 as stable code were merged in the Linux 2.6.28 source code repositories, denoting the end of the development phas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux
Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, packaged as a Linux distribution (distro), which includes the kernel and supporting system software and library (computing), libraries—most of which are provided by third parties—to create a complete operating system, designed as a clone of Unix and released under the copyleft GPL license. List of Linux distributions, Thousands of Linux distributions exist, many based directly or indirectly on other distributions; popular Linux distributions include Debian, Fedora Linux, Linux Mint, Arch Linux, and Ubuntu, while commercial distributions include Red Hat Enterprise Linux, SUSE Linux Enterprise, and ChromeOS. Linux distributions are frequently used in server platforms. Many Linux distributions use the word "Linux" in their name, but the Free ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flash Translation Layer
A flash memory controller (or flash controller) manages data stored on flash memory (usually NAND flash) and communicates with a computer or electronic device. Flash memory controllers can be designed for operating in low duty-cycle environments like memory cards, or other similar media for use in PDAs, mobile phones, etc. USB flash drives use flash memory controllers designed to communicate with personal computers through the USB port at a low duty-cycle. Flash controllers can also be designed for higher duty-cycle environments like solid-state drives (SSDs) used as data storage for laptop computer systems up to mission-critical enterprise storage arrays. Initial setup After a flash storage device is initially manufactured, the flash controller is first used to format the flash memory. This ensures the device is operating properly, it maps out bad flash memory cells, and it allocates spare cells to be substituted for future failed cells. Some part of the spare cells is also u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resource Starvation
In computer science, resource starvation is a problem encountered in concurrent computing where a process is perpetually denied necessary resources ''Resource'' refers to all the materials available in our environment which are Technology, technologically accessible, Economics, economically feasible and Culture, culturally Sustainability, sustainable and help us to satisfy our needs and want ... to process its work. Starvation may be caused by errors in a scheduling or mutual exclusion algorithm, but can also be caused by resource leaks, and can be intentionally caused via a denial-of-service attack such as a fork bomb. When starvation is impossible in a concurrent algorithm, the algorithm is called starvation-free, lockout-freed or said to have finite bypass. This property is an instance of liveness, and is one of the two requirements for any mutual exclusion algorithm; the other being correctness. The name "finite bypass" means that any process (concurrent part) of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Native Command Queuing
In computing, Native Command Queuing (NCQ) is an extension of the Serial ATA protocol allowing hard disk drives to internally optimize the order in which received read and write commands are executed. This can reduce the amount of unnecessary drive head movement, resulting in increased performance (and slightly decreased wear of the drive) for workloads where multiple simultaneous read/write requests are outstanding, most often occurring in Server (computing), server-type applications. History Native Command Queuing was preceded by Parallel ATA's version of Tagged Command Queuing (TCQ). ATA's attempt at integrating TCQ was constrained by the requirement that ATA host bus adapters use Industry Standard Architecture, ISA bus device protocols to interact with the operating system. The resulting high CPU overhead and negligible performance gain contributed to a lack of market acceptance for ATA TCQ. NCQ differs from TCQ in that, with NCQ, each command is of equal importance, but NCQ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Write Barrier
In operating systems, write barrier is a mechanism for enforcing a particular ordering in a sequence of writes to a storage system in a computer system. For example, a write barrier in a file system is a mechanism (program logic) that ensures that in-memory file system state is written out to persistent storage in the correct order. In garbage collection A write barrier in a garbage collector is a fragment of code emitted by the compiler immediately before every store operation to ensure that (e.g.) generational invariants are maintained. In computer storage A write barrier in a memory system, also known as a memory barrier, is a hardware-specific compiler intrinsic that ensures that all preceding memory operations "happen before" all subsequent ones. See also * Native Command Queuing In computing, Native Command Queuing (NCQ) is an extension of the Serial ATA protocol allowing hard disk drives to internally optimize the order in which received read and write commands ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RAID Controller
A disk array controller is a device that manages the physical disk drives Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are cons ... and presents them to the computer as logical units. It often implements hardware RAID, thus it is sometimes referred to as RAID controller. It also often provides additional disk cache (computing), cache. ''Disk array controller'' is often ambiguously shortened to ''disk controller'' which can also refer to the circuitry responsible for managing internal disk drive operations. Front-end and back-end side A disk array controller provides front-end interfaces and back-end interfaces. * The back-end interface communicates with the controlled disks. Hence, its protocol is usually Advanced Technology Attachment, ATA (a.k.a. PATA), Serial ATA, SATA, SCSI, Fibre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
