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39-622: (Redirected from AfS ) AFS is an initialism that may refer to: Computing [ edit ] Andrew File System , a distributed networked file system OpenAFS , an open source implementation of the Andrew File System Apple File Service, implementing the Apple Filing Protocol Apple File System , Apple's proprietary file system AtheOS File System , part of

78-482: A US company Allergic fungal sinusitis Alternative financial service American Foursquare , a style of house Atomic fluorescence spectroscopy Available for sale , an accounting term International Convention on the Control of Harmful Anti-fouling Systems on Ships , 2001 "AFS", a song by Natanael Cano from Nata Montana , 2023 Nikon AF-S, a type of Nikon F-mount lens Topics referred to by

117-424: A device, device type, directory prefix, file path separator, or file type. File systems typically support organizing files into directories , also called folders , which segregate files into groups. This may be implemented by associating the file name with an index in a table of contents or an inode in a Unix-like file system. Directory structures may be flat (i.e. linear), or allow hierarchies by allowing

156-672: A directory to contain directories, called subdirectories. The first file system to support arbitrary hierarchies of directories was used in the Multics operating system. The native file systems of Unix-like systems also support arbitrary directory hierarchies, as do, Apple 's Hierarchical File System and its successor HFS+ in classic Mac OS , the FAT file system in MS-DOS 2.0 and later versions of MS-DOS and in Microsoft Windows ,

195-443: A file system creates a file, it allocates space for data. Some file systems permit or require specifying an initial space allocation and subsequent incremental allocations as the file grows. To delete a file, the file system records that the file's space is free; available to use for another file. A local file system manages storage space to provide a level of reliability and efficiency. Generally, it allocates storage device space in

234-422: A file system implementation. The physical file system layer provides relatively low-level access to a storage device (e.g. disk). It reads and writes data blocks , provides buffering and other memory management and controls placement of blocks in specific locations on the storage medium. This layer uses device drivers or channel I/O to drive the storage device. A file name , or filename , identifies

273-417: A file to consuming applications and in some cases users. A file name is unique so that an application can refer to exactly one file for a particular name. If the file system supports directories, then generally file name uniqueness is enforced within the context of each directory. In other words, a storage can contain multiple files with the same name, but not in the same directory. Most file systems restrict

312-706: A forked file system on the Macintosh, and Microsoft supports streams in NTFS. Some file systems maintain multiple past revisions of a file under a single file name; the file name by itself retrieves the most recent version, while prior saved version can be accessed using a special naming convention such as "filename;4" or "filename(-4)" to access the version four saves ago. See comparison of file systems#Metadata for details on which file systems support which kinds of metadata. A local file system tracks which areas of storage belong to which file and which are not being used. When

351-477: A granular manner, usually multiple physical units (i.e. bytes ). For example, in Apple DOS of the early 1980s, 256-byte sectors on 140 kilobyte floppy disk used a track/sector map . The granular nature results in unused space, sometimes called slack space , for each file except for those that have the rare size that is a multiple of the granular allocation. For a 512-byte allocation, the average unused space

390-992: A political party in Sweden American Folklore Society American Foundry Society Arbeitsstelle für Standardisierung (AfS), a workgroup of the German National Library (DNB) Association of Football Statisticians , UK Australian Flag Society Auxiliary Fire Service , UK and Ireland Places [ edit ] Afs, Idlib , a Syrian village Ashford railway station (Surrey) (station code:AFS), Middlesex, UK South Africa , ITU country code Other [ edit ] Advanced front-lighting system (AFS) or Adaptative Front-lighting System, for automotive headlamps Aeronautical fixed service , for air navigation Afghan afghani , unit of currency Afro-Seminole Creole language (ISO 639-3: oafs) AFS Trinity ,

429-411: A read-only volume, a client system will retrieve data from a particular read-only copy. If at some point, that copy becomes unavailable, clients will look for any of the remaining copies. Again, users of that data are unaware of the location of the read-only copy; administrators can create and relocate such copies as needed. The AFS command suite guarantees that all read-only volumes contain exact copies of

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468-429: A single file per mailbox, like mbox . See AFS and buffered I/O Problems for handling shared databases. A significant feature of AFS is the volume , a tree of files, sub-directories and AFS mountpoints (links to other AFS volumes). Volumes are created by administrators and linked at a specific named path in an AFS cell. Once created, users of the filesystem may create directories and files as usual without concern for

507-431: A stream of bytes . Typically, to read file data, a program provides a memory buffer and the file system retrieves data from the medium and then writes the data to the buffer. A write involves the program providing a buffer of bytes that the file system reads and then stores to the medium. Some file systems, or layers on top of a file system, allow a program to define a record so that a program can read and write data as

546-585: A structure; not an unorganized sequence of bytes. If a fixed length record definition is used, then locating the n record can be calculated mathematically, which is relatively fast compared to parsing the data for record separators. An identification for each record, also known as a key, allows a program to read, write and update records without regard to their location in storage. Such storage requires managing blocks of media, usually separating key blocks and data blocks. Efficient algorithms can be developed with pyramid structures for locating records. Typically,

585-432: A user's use of storage space. A file system typically ensures that stored data remains consistent in both normal operations as well as exceptional situations like: Recovery from exceptional situations may include updating metadata, directory entries and handling data that was buffered but not written to storage media. A file system might record events to allow analysis of issues such as: Many file systems access data as

624-405: Is 256 bytes. For 64 KB clusters, the average unused space is 32 KB. Generally, the allocation unit size is set when the storage is configured. Choosing a relatively small size compared to the files stored, results in excessive access overhead. Choosing a relatively large size results in excessive unused space. Choosing an allocation size based on the average size of files expected to be in

663-848: Is a capability of an operating system that services the applications running on the same computer . A distributed file system is a protocol that provides file access between networked computers. A file system provides a data storage service that allows applications to share mass storage . Without a file system, applications could access the storage in incompatible ways that lead to resource contention , data corruption and data loss . There are many file system designs and implementations – with various structure and features and various resulting characteristics such as speed, flexibility, security, size and more. Files systems have been developed for many types of storage devices , including hard disk drives (HDDs), solid-state drives (SSDs), magnetic tapes and optical discs . A portion of

702-471: Is a fairly simple implementation still incomplete as of January 2024 . The following Access Control List (ACL) permissions can be granted: Permissions that affect files and subdirectories include: Additionally, AFS includes Application ACLs (A)-(H) which have no effect on access to files. File system In computing , a file system or filesystem (often abbreviated to FS or fs ) governs file organization and access. A local file system

741-474: Is different from Wikidata All article disambiguation pages All disambiguation pages Andrew File System AFS has several benefits over traditional networked file systems , particularly in the areas of security and scalability. One enterprise AFS deployment at Morgan Stanley exceeds 25,000 clients. AFS uses Kerberos for authentication, and implements access control lists on directories for users and groups. Each client caches files on

780-534: Is invisible to the end user and the system still works correctly. However this can degrade performance on some storage hardware that work better with contiguous blocks such as hard disk drives . Other hardware such as solid-state drives are not affected by fragmentation. A file system often supports access control of data that it manages. The intent of access control is often to prevent certain users from reading or modifying certain files. Access control can also restrict access by program in order to ensure that data

819-406: Is maintained by callback mechanism. When a file is cached, the server makes a note of this and promises to inform the client if the file is updated by someone else. Callbacks are discarded and must be re-established after any client, server, or network failure, including a timeout. Re-establishing a callback involves a status check and does not require re-reading the file itself. A consequence of

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858-510: Is modified in a controlled way. Examples include passwords stored in the metadata of the file or elsewhere and file permissions in the form of permission bits, access control lists , or capabilities . The need for file system utilities to be able to access the data at the media level to reorganize the structures and provide efficient backup usually means that these are only effective for polite users but are not effective against intruders. Methods for encrypting file data are sometimes included in

897-550: Is stored inside the allocation group itself. Additional attributes can be associated on file systems, such as NTFS , XFS , ext2 , ext3 , some versions of UFS , and HFS+ , using extended file attributes . Some file systems provide for user defined attributes such as the author of the document, the character encoding of a document or the size of an image. Some file systems allow for different data collections to be associated with one file name. These separate collections may be referred to as streams or forks . Apple has long used

936-680: The NTFS file system in the Windows NT family of operating systems, and the ODS-2 (On-Disk Structure-2) and higher levels of the Files-11 file system in OpenVMS . In addition to data, the file content, a file system also manages associated metadata which may include but is not limited to: A file system stores associated metadata separate from the content of the file. Most file systems store

975-543: The file locking strategy is that AFS does not support large shared databases or record updating within files shared between client systems. This was a deliberate design decision based on the perceived needs of the university computing environment. For example, in the original email system for the Andrew Project, the Andrew Message System, a single file per message is used, like maildir , rather than

1014-534: The Syllable operating system Education [ edit ] AFS Intercultural Programs , formerly American Field Service Abington Friends School , in Jenkintown, Pennsylvania, United States Military [ edit ] Army Fire Service , UK Air force station A US Navy hull classification symbol: Combat Stores Ship (AFS) Organizations [ edit ] Alternative for Sweden ,

1053-421: The computer main memory can be set up as a RAM disk that serves as a storage device for a file system. File systems such as tmpfs can store files in virtual memory . A virtual file system provides access to files that are either computed on request, called virtual files (see procfs and sysfs ), or are mapping into another, backing storage. From c.  1900 and before the advent of computers

1092-519: The concepts. The logical file system layer provides relatively high-level access via an application programming interface (API) for file operations including open, close, read and write – delegating operations to lower layers. This layer manages open file table entries and per-process file descriptors. It provides file access, directory operations, security and protection. The virtual file system , an optional layer, supports multiple concurrent instances of physical file systems, each of which called

1131-416: The file system. This is very effective since there is no need for file system utilities to know the encryption seed to effectively manage the data. The risks of relying on encryption include the fact that an attacker can copy the data and use brute force to decrypt the data. Additionally, losing the seed means losing the data. Some operating systems allow a system administrator to enable disk quotas to limit

1170-500: The length of a file name. Some file systems match file names as case sensitive and others as case insensitive. For example, the names MYFILE and myfile match the same file for case insensitive, but different files for case sensitive. Most modern file systems allow a file name to contain a wide range of characters from the Unicode character set. Some restrict characters such as those used to indicate special attributes such as

1209-419: The local filesystem for increased speed on subsequent requests for the same file. This also allows limited filesystem access in the event of a server crash or a network outage . AFS uses the weak consistency model. Read and write operations on an open file are directed only to the locally cached copy. When a modified file is closed, the changed portions are copied back to the file server. Cache consistency

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1248-595: The names of all the files in one directory in one place—the directory table for that directory—which is often stored like any other file. Many file systems put only some of the metadata for a file in the directory table, and the rest of the metadata for that file in a completely separate structure, such as the inode . Most file systems also store metadata not associated with any one particular file. Such metadata includes information about unused regions— free space bitmap , block availability map —and information about bad sectors . Often such information about an allocation group

1287-486: The original read-write volume at the time the read-only copy was created. The file name space on an Andrew workstation is partitioned into a shared and local name space. The shared name space (usually mounted as /afs on the Unix filesystem) is identical on all workstations. The local name space is unique to each workstation. It only contains temporary files needed for workstation initialization and symbolic links to files in

1326-652: The original, a few other implementations were developed. OpenAFS was built from source released by Transarc ( IBM ) in 2000. Transarc software became deprecated and lost support. Arla was an independent implementation of AFS developed at the Royal Institute of Technology in Stockholm in the late 1990s and early 2000s. A fourth implementation of an AFS client exists in the Linux kernel source code since at least version 2.6.10. Committed by Red Hat , this

1365-405: The physical location of the volume. A volume may have a quota assigned to it in order to limit the amount of space consumed. As needed, AFS administrators can move that volume to another server and disk location without the need to notify users; the operation can even occur while files in that volume are being used. AFS volumes can be replicated to read-only cloned copies. When accessing files in

1404-449: The same term [REDACTED] This disambiguation page lists articles associated with the title AFS . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=AFS&oldid=1249607035 " Category : Disambiguation pages Hidden categories: Articles containing German-language text Short description

1443-605: The shared name space. The Andrew File System heavily influenced Version 4 of Sun Microsystems ' popular Network File System (NFS). Additionally, a variant of AFS, the DCE Distributed File System (DFS) was adopted by the Open Software Foundation in 1989 as part of their Distributed Computing Environment . Finally AFS (version two) was the predecessor of the Coda file system. Besides

1482-429: The storage tends to minimize unusable space. As a file system creates, modifies and deletes files, the underlying storage representation may become fragmented . Files and the unused space between files will occupy allocation blocks that are not contiguous. A file becomes fragmented if space needed to store its content cannot be allocated in contiguous blocks. Free space becomes fragmented when files are deleted. This

1521-442: The terms file system , filing system and system for filing were used to describe methods of organizing, storing and retrieving paper documents. By 1961, the term file system was being applied to computerized filing alongside the original meaning. By 1964, it was in general use. A local file system's architecture can be described as layers of abstraction even though a particular file system design may not actually separate

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