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Linux MD RAID
mdadm is a Linux utility used to manage and monitor software RAID devices. It is used in modern Linux distributions in place of older software RAID utilities such as raidtools2 or raidtools. mdadm is free software originally maintained by, and copyrighted to, Neil Brown of SUSE, and licensed under the terms of version 2 or later of the GNU General Public License. Name The name is derived from the ''md'' (multiple device) device nodes it ''administers'' or manages, and it replaced a previous utility ''mdctl''. The original name was "Mirror Disk", but was changed as more functions were added. The name is now understood to be short for Multiple Disk and Device Management. Overview Linux software RAID configurations can include anything presented to the Linux kernel as a block device. This includes whole hard drives (for example, ), and their partitions (for example, ). RAID configurations * ''RAID 0'' – Block-level striping. MD can handle devices of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C (programming Language)
C (''pronounced'' '' – like the letter c'') is a general-purpose programming language. It was created in the 1970s by Dennis Ritchie and remains very widely used and influential. By design, C's features cleanly reflect the capabilities of the targeted Central processing unit, CPUs. It has found lasting use in operating systems code (especially in Kernel (operating system), kernels), device drivers, and protocol stacks, but its use in application software has been decreasing. C is commonly used on computer architectures that range from the largest supercomputers to the smallest microcontrollers and embedded systems. A successor to the programming language B (programming language), B, C was originally developed at Bell Labs by Ritchie between 1972 and 1973 to construct utilities running on Unix. It was applied to re-implementing the kernel of the Unix operating system. During the 1980s, C gradually gained popularity. It has become one of the most widely used programming langu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Degraded Mode
When a RAID array experiences the failure of one or more disks, it can enter degraded mode, a fallback mode that generally allows the continued usage of the array, but either loses the performance boosts of the RAID technique (such as a RAID-1 mirror across two disks when one of them fails; performance will fall back to that of a normal, single drive) or experiences severe performance penalties due to the necessity to reconstruct the damaged data from error correction data. Depending on the severity of the problem, the array may be placed into a ''read-only'' mode, either automatically or by the system administrator An IT administrator, system administrator, sysadmin, or admin is a person who is responsible for the upkeep, configuration, and reliable operation of computer systems, especially multi-user computers, such as Server (computing), servers. The ..., until it can be corrected. Such corrections may or may not be possible to do ''on-line'' (as opposed to an "off-lin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intel Rapid Storage Technology
Intel Rapid Storage Technology (RST) is a driver SATA AHCI and a firmware-based RAID solution built into a wide range of Intel chipsets. Currently also is installed as a driver for Intel Optane temporary storage units. It contains two operation modes that follow two Intel specific modes rather than the SATA standard. The name modes and the application that contains them have been renamed since the first version. Until 2010 it contains AHCI and Matrix RAID modes. The first mode is the Intel driver SATA normal and the latter mode is a fake RAID. Up to version 4 it is included on Intel Application Accelerator RAID Edition, between versions 5 and 8.9 it is included on Intel Matrix Storage Manager (IMSM), since version 9 it is included on Intel Rapid Storage Technology (IRST) preferring the driver modes to be named RST AHCI and RST AHCI RAID instead of Matrix RAID. The latter is also known as RST RAID mode, since it is the mode that Intel recommends to use, even if you are not work ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Storage Networking Industry Association
The Storage Networking Industry Association (SNIA) is an American trade association, incorporated in December 1997. It is a registered 501(c)(6) non-profit organization. SNIA has more than 185 unique members, 2,000 active contributing members, and over 50,000 IT end users and storage professionals. Description SNIA's membership community participates in the following storage-related technical working groups: * Cloud Storage Technologies * Computational Storage * Data Management * Data Security * Dictionary * DNA Data Storage * Networked Storage * Next Generation Data Center * Persistent Memory * Physical Storage * Power Efficiency Measurement * Storage Management Initiative – Specification (SMI-S) * SNIA Swordfish® - Scalable Storage Management Specificati SNIA and its technical council maintain a vendor-neutral dictionary and glossary of storage networking, data, and information management terminology. The SNIA dictionary won an award for publication excellence in 2009 and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fake RAID
RAID (; redundant array of inexpensive disks or redundant array of independent disks) is a data storage virtualization technology that combines multiple physical data storage components into one or more logical units for the purposes of data redundancy, performance improvement, or both. This is in contrast to the previous concept of highly reliable mainframe disk drives known as ''single large expensive disk'' (''SLED''). Data is distributed across the drives in one of several ways, referred to as RAID levels, depending on the required level of redundancy and performance. The different schemes, or data distribution layouts, are named by the word "RAID" followed by a number, for example RAID 0 or RAID 1. Each scheme, or RAID level, provides a different balance among the key goals: reliability, availability, performance, and capacity. RAID levels greater than RAID 0 provide protection against unrecoverable sector read errors, as well as against failures of whole phy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initramfs
In Linux systems, initrd (''initial ramdisk'') is a scheme for loading a temporary root file system into memory, to be used as part of the Linux startup process. initrd and initramfs (from INITial RAM File System) refer to two different methods of achieving this. Both are commonly used to make preparations before the real root file system can be mounted. Rationale Many Linux distributions ship a single, generic Linux kernel image one which the distribution's developers create specifically to boot on a wide variety of hardware. The device drivers for this generic kernel image are included as loadable kernel modules because statically compiling many drivers into one kernel causes the kernel image to be much larger, perhaps too large to boot on computers with limited memory, or in some cases to cause boot-time crashes or other problems due to probing for nonexistent or conflicting hardware. This static-compiled kernel approach also leaves modules in kernel memory which are no longer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
/boot
In Unix-like operating systems, a boot folder is the directory which holds files used in booting the operating system, typically . The usage is standardized within Linux in the Filesystem Hierarchy Standard. Contents The contents are mostly Linux kernel files or boot loader files, depending on the boot loader, most commonly (on Linux) LILO or GRUB. Linux * vmlinux – the Linux kernel * initrd.img – a temporary file system, used prior to loading the kernel * System.map – a symbol lookup table LILO LILO creates and uses the following files: * map – a key file, which records where files needed by LILO during boot are stored. Following kernel upgrades, this file must be regenerated by running the "map installer", which is otherwise the system will not boot. * boot.''xxyy'' – these 512-byte files are backups of boot sectors, either the master boot record (MBR) or volume boot record (VBR), created when LILO overwrites a boot sector. ''xx'' and ''yy'' are the major and mi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GNU GRUB
GNU GRUB (short for GNU GRand Unified Bootloader, commonly referred to as GRUB) is a boot loader package from the GNU Project. GRUB is the reference implementation of the Free Software Foundation's Multiboot Specification, which provides a user the choice to boot one of multiple operating systems installed on a computer set up for multi-booting or select a specific Kernel (operating system), kernel configuration available on a particular operating system's partitions. GNU GRUB was developed from a package called the ''Grand Unified Bootloader'' (a play on Grand Unified Theory). It is predominantly used for Unix-like systems. Operation Booting When a computer is turned on, its BIOS finds the primary bootable device (usually the computer's hard disk) and runs the initial Bootstrapping (computing), bootstrap program from the master boot record (MBR). The MBR is the first Disk sector, sector of the hard disk. This bootstrap program must be small because it has to fit in a sin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LILO (boot Loader)
LILO (Linux Loader) is a bootloader for Linux and was the default boot loader for most Linux distributions . Unlike loadlin, it allowed booting Linux without having DOS on the computer. As of 2009, most distributions have switched to GRUB as the default boot loader. Further development of LILO was discontinued in December 2015 along with a request by Joachim Wiedorn for potential developers. ELILO For EFI-based PC hardware the now orphaned ELILO boot loader was developed, originally by Hewlett-Packard for IA-64 systems, but later also for standard i386 The Intel 386, originally released as the 80386 and later renamed i386, is the third-generation x86 architecture microprocessor from Intel. It was the first 32-bit processor in the line, making it a significant evolution in the x86 archite ... and amd64 hardware with EFI support. On any version of Linux running on Intel-based Apple Macintosh hardware, ELILO is one of the available bootloaders. It supports ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solid-state Drive
A solid-state drive (SSD) is a type of solid-state storage device that uses integrated circuits to store data persistently. It is sometimes called semiconductor storage device, solid-state device, or solid-state disk. SSDs rely on non-volatile memory, typically NAND flash, to store data in memory cells. The performance and endurance of SSDs vary depending on the number of bits stored per cell, ranging from high-performing single-level cells (SLC) to more affordable but slower quad-level cells (QLC). In addition to flash-based SSDs, other technologies such as 3D XPoint offer faster speeds and higher endurance through different data storage mechanisms. Unlike traditional hard disk drives (HDDs), SSDs have no moving parts, allowing them to deliver faster data access speeds, reduced latency, increased resistance to physical shock, lower power consumption, and silent operation. Often interfaced to a system in the same way as HDDs, SSDs are used in a variety of devices, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trim (computing)
A trim command (known as TRIM in the ATA command set, and UNMAP in the SCSI command set) allows an operating system to inform a solid-state drive (SSD) which blocks of data are no longer considered to be "in use" and therefore can be erased internally. Trim was introduced soon after SSDs were introduced. Because low-level operation of SSDs differs significantly from hard drives, the conventional manner in which operating systems handle storage operations—such as deletions and formatting—resulted in unanticipated progressive performance degradation of write operations on SSDs. Trimming enables the SSD to more efficiently handle garbage collection, which would otherwise slow future write operations to the involved blocks.Shimpi, Anand Lal. (18 March 2009). p. 10. TRIM is an ATA command (Advanced Technology Attachment Command) that allows an OS to inform SSD about the blocks of data no longer in use. The SSD then deletes such blocks of data to make a way for newer blocks of da ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
