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WAPBL
__NOTOC__ Write Ahead Physical Block Logging (WAPBL) provides meta data journaling for file systems in conjunction with Fast File System (FFS) to accomplish rapid filesystem consistency after an unclean shutdown of the filesystem and better general use performance over regular FFS. With the journal, fsck is no longer required at system boot; instead, the system can replay the journal in order to correct any inconsistencies in the filesystem if the system has been shut down in an unclean fashion. History WAPBL was initially committed into NetBSD in 2008, and first appeared with NetBSD 5.0 (2009). With NetBSD 6.0 (2012), ''soft updates'' (known as ''soft dependencies'' in NetBSD) was removed in favour of ''WAPBL''. See also * Log-structured file system * Soft updates * Unix File System The Unix file system (UFS) is a family of file systems supported by many Unix and Unix-like operating systems. It is a distant descendant of the original filesystem used by Version 7 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NetBSD
NetBSD is a free and open-source Unix-like operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was fork (software development), forked. It continues to be actively developed and is available for many platforms, including servers, desktops, handheld devices, and embedded systems. The NetBSD project focuses on code clarity, careful design, and portability across many computer architectures. Its source code is publicly available and Permissive free software licence, permissively licensed. History NetBSD was originally derived from the 4.3BSD-Reno release of the Berkeley Software Distribution from the Computer Systems Research Group of the University of California, Berkeley, via its Net/2 source code release and the 386BSD project. The NetBSD project began as a result of frustration within the 386BSD developer community with the pace and direction of the operating system's development. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unix File System
The Unix file system (UFS) is a family of file systems supported by many Unix and Unix-like operating systems. It is a distant descendant of the original filesystem used by Version 7 Unix. Design A UFS volume is composed of the following parts: * A few blocks at the beginning of the partition reserved for boot blocks (which must be initialized separately from the filesystem) * A superblock, containing a magic number identifying this as a UFS filesystem, and some other vital numbers describing this filesystem's geometry and statistics and behavioral tuning parameters * A collection of cylinder groups. Each cylinder group has the following components: ** A backup copy of the superblock ** A cylinder group header, with statistics, free lists, etc., about this cylinder group, similar to those in the superblock ** A number of inodes, each containing file attributes ** A number of data blocks Inodes are numbered sequentially, starting at 0. Inode 0 is reserved for unalloc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soft Updates
Soft updates is an approach to maintaining file system metadata integrity in the event of a crash or power outage. Soft updates work by tracking and enforcing dependencies among updates to file system metadata. Soft updates are an alternative to the more commonly used approach of journaling file systems. Method of operation Soft updates allow only asynchronous metadata writes that do not render the on-disk file system inconsistent, or that the only inconsistency that ever happens is a storage space leak (space marked allocated when not used by any file). It avoids having to do ordered synchronous metadata writes by temporarily "rolling back" any part of a metadata block that depends on another potentially non-flushed or partially rolled-back block when writing it. In effect, blocks may be flushed at any time and the soft updates code will always provide the disk a consistent version of the metadata (as long as it knows which blocks have physically been flushed). Recovery th ... [...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 subsequentl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fsck
The system utility fsck (''file system check'') is a tool for checking the consistency of a file system in Unix and Unix-like operating systems, such as 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, pac ..., macOS, and FreeBSD. "In actuality, fsck is simply a front-end for the various filesystem checkers (fsck.fstype) available under Linux." The equivalent programs on MS-DOS and Microsoft Windows are CHKDSK, System File Checker, SFC, and SCANDISK. Use Generally, fsck is run either automatically at boot time, or manually by the system administrator. The command works directly on data structures stored on disk, which are internal and specific to the particular file system in use - so an fsck command tailored to the file system is generally required. The exact behaviors of variou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Log-structured File System
A log-structured filesystem is a file system in which data and metadata are written sequentially to a circular buffer, called a log. The design was first proposed in 1988 by John K. Ousterhout and Fred Douglis and first implemented in 1992 by Ousterhout and Mendel Rosenblum for the Unix-like Sprite distributed operating system. Rationale Conventional file systems lay out files with great care for spatial locality and make in-place changes to their data structures in order to perform well on optical and magnetic disks, which tend to seek relatively slowly. The design of log-structured file systems is based on the hypothesis that this will no longer be effective because ever-increasing memory sizes on modern computers would lead to I/O becoming write-heavy since reads would be almost always satisfied from memory cache. A log-structured file system thus treats its storage as a circular log and writes sequentially to the head of the log. This has several important side effe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
O'Reilly Media
O'Reilly Media, Inc. (formerly O'Reilly & Associates) is an American learning company established by Tim O'Reilly that provides technical and professional skills development courses via an online learning platform. O'Reilly also publishes books about programming and other technical content. Its distinctive brand features a woodcut of an animal on many of its book covers. The company was known as a popular tech conference organizer for more than 20 years before closing the live conferences arm of its business. Company Early days The company began in 1978 as a private consulting firm doing technical writing, based in the Cambridge, Massachusetts area. In 1984, it began to retain publishing rights on manuals created for Unix vendors. A few 70-page "Nutshell Handbooks" were well-received, but the focus remained on the consulting business until 1988. After a conference displaying O'Reilly's preliminary Xlib manuals attracted significant attention, the company began increas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer File Systems
A computer is a machine that can be programmed to automatically carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic sets of operations known as ''programs'', which enable computers to perform a wide range of tasks. The term computer system may refer to a nominally complete computer that includes the hardware, operating system, software, and peripheral equipment needed and used for full operation; or to a group of computers that are linked and function together, such as a computer network or computer cluster. A broad range of industrial and consumer products use computers as control systems, including simple special-purpose devices like microwave ovens and remote controls, and factory devices like industrial robots. Computers are at the core of general-purpose devices such as personal computers and mobile devices such as smartphones. Computers power the Internet, which links billions of computer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
