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XFS
XFS is a high-performance 64-bit journaling file system created by Silicon Graphics, Inc (SGI) in 1993. It was the default file system in SGI's IRIX operating system starting with its version 5.3. XFS was ported to the Linux kernel in 2001; as of June 2014, XFS is supported by most Linux distributions; Red Hat Enterprise Linux uses it as default filesystem. XFS excels in the execution of parallel input/output (I/O) operations due to its design, which is based on allocation groups (a type of subdivision of the physical volumes in which XFS is used- also shortened to ''AGs''). Because of this, XFS enables extreme scalability of I/O threads, file system bandwidth, and size of files and of the file system itself when spanning multiple physical storage devices. XFS ensures the consistency of data by employing metadata journaling and supporting write barriers. Space allocation is performed via extents with data structures stored in B+ trees, improving the overall performance of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IRIX
IRIX ( ) is a discontinued operating system developed by Silicon Graphics (SGI) to run on the company's proprietary MIPS workstations and servers. It is based on UNIX System V with BSD extensions. In IRIX, SGI originated the XFS file system and the industry-standard OpenGL graphics system. History SGI originated the IRIX name in the 1988 release 3.0 of the operating system for the SGI IRIS 4D series of workstations and servers. Previous releases are identified only by the release number prefixed by "4D1-", such as "4D1-2.2". The "4D1-" prefix continued to be used in official documentation to prefix IRIX release numbers. Prior to the IRIS 4D, SGI bundled the GL2 operating system, based on UniSoft UniPlus System V Unix, and using the proprietary MEX (Multiple EXposure) windowing system. IRIX 3.x is based on UNIX System V Release 3 with 4.3BSD enhancements, and incorporates the 4Sight windowing system, based on NeWS and IRIS GL. SGI's own Extent File System (EFS) replaces t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux Kernel
The Linux kernel is a free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally authored in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU operating system, which was written to be a free (libre) replacement for Unix. Linux is provided under the GNU General Public License version 2 only, but it contains files under other compatible licenses. Since the late 1990s, it has been included as part of a large number of operating system distributions, many of which are commonly also called Linux. Linux is deployed on a wide variety of computing systems, such as embedded devices, mobile devices (including its use in the Android operating system), personal computers, servers, mainframes, and supercomputers. It can be tailored for specific architectures and for several usage scenarios using a family of simple commands (that is, without the need of manually editing its source c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux Kernel Mainline
The Linux kernel is a free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally authored in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU operating system, which was written to be a free (libre) replacement for Unix. Linux is provided under the GNU General Public License version 2 only, but it contains files under other compatible licenses. Since the late 1990s, it has been included as part of a large number of operating system distributions, many of which are commonly also called Linux. Linux is deployed on a wide variety of computing systems, such as embedded devices, mobile devices (including its use in the Android operating system), personal computers, servers, mainframes, and supercomputers. It can be tailored for specific architectures and for several usage scenarios using a family of simple commands (that is, without the need of manually editing its source co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allocation Group
An AG or allocation group is a subvolume in a file system which maintains its own track of free blocks and file data. This makes simultaneous file operations possible; only one write can happen to an AG at any time, but multiple operations can be performed on the file system, each happening in a different AG. In SMP systems, multiple CPUs can write to different AGs, enabling physically concurrent disk operations on a single file system. Whereas a single hard disk is not capable of reading or writing to multiple places simultaneously, a file system or partition that utilizes a scheme such as RAID or logical volume management may encompass multiple physical disks. In this case, the use of allocation groups may grant additional file system throughput. Allocation groups are used by these file systems: * XFS from SGI, an XFS AG can have a max size of 1TiB * Btrfs * JFS * ext2, ext3 and ext4 ext4 (fourth extended filesystem) is a journaling file system for Linux, developed as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicon Graphics
Silicon Graphics, Inc. (stylized as SiliconGraphics before 1999, later rebranded SGI, historically known as Silicon Graphics Computer Systems or SGCS) was an American high-performance computing manufacturer, producing computer hardware and software. Founded in Mountain View, California in November 1981 by Jim Clark, its initial market was 3D graphics computer workstations, but its products, strategies and market positions developed significantly over time. Early systems were based on the Geometry Engine that Clark and Marc Hannah had developed at Stanford University, and were derived from Clark's broader background in computer graphics. The Geometry Engine was the first very-large-scale integration (VLSI) implementation of a geometry pipeline, specialized hardware that accelerated the "inner-loop" geometric computations needed to display three-dimensional images. For much of its history, the company focused on 3D imaging and was a major supplier of both hardware and softwa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delayed Allocation
Allocate-on-flush (also called delayed allocation) is a file system feature implemented in HFS+, XFS, Reiser4, ZFS, Btrfs, and ext4. The feature also closely resembles an older technique that Berkeley's UFS called "block reallocation". When blocks must be allocated to hold pending writes, disk space for the appended data is subtracted from the free-space counter, but not actually allocated in the free-space bitmap Free-space bitmaps are one method used to track allocated sectors by some file systems. While the most simplistic design is highly inefficient, advanced or hybrid implementations of free-space bitmaps are used by some modern file systems. Exampl .... Instead, the appended data are held in memory until they must be flushed to storage due to memory pressure, when the kernel decides to flush dirty buffers, or when the application performs the Unix ''sync'' system call, for example. This has the effect of batching together allocations into larger runs. Such delayed p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
B+ Tree
A B+ tree is an m-ary tree with a variable but often large number of children per node. A B+ tree consists of a root, internal nodes and leaves. The root may be either a leaf or a node with two or more children. A B+ tree can be viewed as a B-tree in which each node contains only keys (not key–value pairs), and to which an additional level is added at the bottom with linked leaves. The primary value of a B+ tree is in storing data for efficient retrieval in a block-oriented storage context — in particular, filesystems. This is primarily because unlike binary search trees, B+ trees have very high fanout (number of pointers to child nodes in a node, typically on the order of 100 or more), which reduces the number of I/O operations required to find an element in the tree. History There is no single paper introducing the B+ tree concept. Instead, the notion of maintaining all data in leaf nodes is repeatedly brought up as an interesting variant. Douglas Comer notes in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extent (file Systems)
In computing, an extent is a contiguous area of storage reserved for a file in a file system, represented as a range of block numbers, or tracks on count key data devices. A file can consist of zero or more extents; one file fragment requires one extent. The direct benefit is in storing each range compactly as two numbers, instead of canonically storing every block number in the range. Also, extent allocation results in less file fragmentation. Extent-based file systems can also eliminate most of the metadata overhead of large files that would traditionally be taken up by the block-allocation tree. But because the savings are small compared to the amount of stored data (for all file sizes in general) but make up a large portion of the metadata (for large files), the overall benefits in storage efficiency and performance are slight. In order to resist fragmentation, several extent-based file systems do allocate-on-flush. Many modern fault-tolerant file systems also do copy-o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Defragmentation
In the maintenance of file systems, defragmentation is a process that reduces the degree of fragmentation. It does this by physically organizing the contents of the mass storage device used to store files into the smallest number of contiguous regions (fragments, ''extents''). It also attempts to create larger regions of free space using compaction to impede the return of fragmentation. Some defragmentation utilities try to keep smaller files within a single directory together, as they are often accessed in sequence. Defragmentation is advantageous and relevant to file systems on electromechanical disk drives (hard disk drives, floppy disk drives and optical disk media). The movement of the hard drive's read/write heads over different areas of the disk when accessing fragmented files is slower, compared to accessing the entire contents of a non-fragmented file sequentially without moving the read/write heads to seek other fragments. Causes of fragmentation Fragmenta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journaling File System
A journaling file system is a file system that keeps track of changes not yet committed to the file system's main part by recording the goal of such changes in a data structure known as a " journal", which is usually a circular log. In the event of a system crash or power failure, such file systems can be brought back online more quickly with a lower likelihood of becoming corrupted. Depending on the actual implementation, a journaling file system may only keep track of stored metadata, resulting in improved performance at the expense of increased possibility for data corruption. Alternatively, a journaling file system may track both stored data and related metadata, while some implementations allow selectable behavior in this regard. History In 1990 IBM introduced JFS in AIX 3.1 as one of the first UNIX commercial filesystems that implemented journaling. The next year the idea was popularized in a widely cited paper on log-structured file systems. This was subsequently i ... [...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 In computing, a memory barrier, also known as a membar, memory fence or fence instruction, is a type of barrier instruction that causes a central processing unit (CPU) or compiler to enforce an ordering constraint on memory operations issued b ..., is a hardware-specific compiler intrinsic that ensures that all preceding memory operations "happen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Patch (computing)
A patch is a set of changes to a computer program or its supporting data designed to update, fix, or improve it. This includes fixing security vulnerabilities and other bugs, with such patches usually being called bugfixes or bug fixes. Patches are often written to improve the functionality, usability, or performance of a program. The majority of patches are provided by software vendors for operating system and application updates. Patches may be installed either under programmed control or by a human programmer using an editing tool or a debugger. They may be applied to program files on a storage device, or in computer memory. Patches may be permanent (until patched again) or temporary. Patching makes possible the modification of compiled and machine language object programs when the source code is unavailable. This demands a thorough understanding of the inner workings of the object code by the person creating the patch, which is difficult without close study of the sourc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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