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Venti
Venti is a network storage system that permanently stores data blocks. A 160-bit SHA-1 hash of the data (called ''score'' by Venti) acts as the address of the data. This enforces a ''write-once'' policy since no other data block can be found with the same address: the addresses of multiple writes of the same data are identical, so duplicate data is easily identified and the data block is stored only once. Data blocks cannot be removed, making it ideal for permanent or backup storage. Venti is typically used with Fossil to provide a file system with permanent snapshots. History Venti was designed and implemented by Sean Quinlan and Sean Dorward at Bell Labs. It appeared in the Plan 9 distribution in 2002. Development has been continued by Russ Cox who has reimplemented most of the server, written a library for creating datastructures (files, directories and meta-data) to store in Venti and implemented optimizations. Venti is available both in the Plan 9 distribution and f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fossil (file System)
Fossil is the default file system in Plan 9 from Bell Labs. It serves the network protocol 9P and runs as a user space daemon, like most Plan 9 file servers. Fossil is different from most other file systems due to its snapshot/archival feature. It can take snapshots of the entire file system on command or automatically (at a user-set interval). These snapshots can be kept on the Fossil partition as long as disk space allows; if the partition fills up then old snapshots will be removed to free up disk space. A snapshot can also be saved permanently to Venti. Fossil and Venti are typically installed together. Features Important features include: *Snapshots are available to all users. No administrator intervention is needed to access old data. (This is possible because Fossil enforces file permissions; users can only access data which they would be allowed to access anyway; thus a user cannot snoop on another's old files or look at old passwords or such.) *Data in permanent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plan 9 From Bell Labs
Plan 9 from Bell Labs is a distributed operating system which originated from the Computing Science Research Center (CSRC) at Bell Labs in the mid-1980s and built on UNIX concepts first developed there in the late 1960s. Since 2000, Plan 9 has been free and open-source. The final official release was in early 2015. Under Plan 9, UNIX's ''everything is a file'' metaphor is extended via a pervasive network-centric filesystem, and the cursor-addressed, terminal-based I/O at the heart of UNIX-like operating systems is replaced by a windowing system and graphical user interface without cursor addressing, although rc, the Plan 9 shell, is text-based. The name ''Plan 9 from Bell Labs'' is a reference to the Ed Wood 1957 cult science fiction Z-movie '' Plan 9 from Outer Space''. The system continues to be used and developed by operating system researchers and hobbyists. History Plan 9 from Bell Labs was originally developed, starting in the late 1980s, by members of the Computing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plan 9 From User Space
Plan 9 from User Space (also plan9port or p9p) is a port of many Plan 9 from Bell Labs libraries and applications to Unix-like operating systems. Currently it has been tested on a variety of operating systems including: Linux, macOS, FreeBSD, NetBSD, OpenBSD, Solaris and SunOS. The project's name is a reference to the 1950s Ed Wood film '' Plan 9 from Outer Space''. A number of key applications have been ported, as have programs used by the system itself, along with the requisite libraries from Plan 9. All of these have been made to work on top of a Unix-like environment instead of their native Plan 9. Some of the most significant ported components are: * rc – The Plan 9 shell. * sam – A text editor. * acme – A combination text editor and graphical shell especially useful to programmers. * mk – A tool for building software, analogous to the traditional Unix make utility. * plumber – An interprocess messaging facility. * Venti Venti is a network storage system that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compact Disc
The compact disc (CD) is a Digital media, digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in October 1982 in Japan and branded as ''Compact Disc Digital Audio, Digital Audio Compact Disc''. The format was later adapted (as CD-ROM) for general-purpose data storage. Several other formats were further derived, including write-once audio and data storage (CD-R), rewritable media (CD-RW), Video CD (VCD), Super Video CD (SVCD), Photo CD, Picture CD, Compact Disc-Interactive (CD-i) and Enhanced Music CD. Standard CDs have a diameter of and are designed to hold up to 74 minutes of uncompressed stereo digital audio or about 650 mebibyte, MiB of data. Capacity is routinely extended to 80 minutes and 700 mebibyte, MiB by arranging data more closely on the same sized disc. The Mini CD has various diameters ranging from ; t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash Tree (persistent Data Structure)
In computer science, a hash tree (or hash trie) is a persistent data structure that can be used to implement sets and maps, intended to replace hash tables in purely functional programming. In its basic form, a hash tree stores the hashes of its keys, regarded as strings of bits, in a trie, with the actual keys and (optional) values stored at the trie's "final" nodes. Hash array mapped tries and Ctrie A concurrent hash-trie or CtrieProkopec, A. et al. (2011Cache-Aware Lock-Free Concurrent Hash Tries Technical Report, 2011.Prokopec, A., Bronson N., Bagwell P., Odersky M. (2012Concurrent Tries with Efficient Non-Blocking Snapshots/ref> is a concu ...s are refined versions of this data structure, using particular type of trie implementations. References Functional data structures Hashing {{compu-prog-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fragmentation (computer)
In computer storage, fragmentation is a phenomenon in which storage space, main storage or secondary storage, is used inefficiently, reducing capacity or performance and often both. The exact consequences of fragmentation depend on the specific system of storage allocation in use and the particular form of fragmentation. In many cases, fragmentation leads to storage space being "wasted", and in that case the term also refers to the wasted space itself. Basic principle When a computer program requests blocks of memory from the computer system, the blocks are allocated in chunks. When the computer program is finished with a chunk, it can free it back to the system, making it available to later be allocated again to another or the same program. The size and the amount of time a chunk is held by a program varies. During its lifespan, a computer program can request and free many chunks of memory. When a program is started, the free memory areas are long and contiguous. Over time and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hard Drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnetic material. The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces. Data is accessed in a random-access manner, meaning that individual blocks of data can be stored and retrieved in any order. HDDs are a type of non-volatile storage, retaining stored data when powered off. Modern HDDs are typically in the form of a small rectangular box. Introduced by IBM in 1956, HDDs were the dominant secondary storage device for general-purpose computers beginning in the early 1960s. HDDs maintained this position into the modern era of servers and personal computers, though personal computing devices produced in large volume, like cell phones and tablets, rely on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Redundant Array Of Independent Disks
Raid, RAID or Raids may refer to: Attack * Raid (military), a sudden attack behind the enemy's lines without the intention of holding ground * Corporate raid, a type of hostile takeover in business * Panty raid, a prankish raid by male college students on the living quarters of female students to steal panties as trophies * Police raid, a police action involving the entering of a house with the intent to capture personnel or evidence, often taking place early in the morning *Union raid, when an outsider trade union takes over the membership of an existing union Arts, entertainment, and media Films * ''Raid'' (1947 film), an East German film * ''Raid'' (2003 film), a 2003 Finnish film * ''Raid'' (2018 film), an Indian period crime thriller Gaming * Raid (gaming), a type of mission in a video game where a large number of people combine forces to defeat a powerful enemy * ''Raid'' (video game), a Nintendo Entertainment System title released by Sachen in 1989 * '' Raid over Mos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SHA-1
In cryptography, SHA-1 (Secure Hash Algorithm 1) is a cryptographically broken but still widely used hash function which takes an input and produces a 160-bit (20-byte) hash value known as a message digest – typically rendered as 40 hexadecimal digits. It was designed by the United States National Security Agency, and is a U.S. Federal Information Processing Standard. Since 2005, SHA-1 has not been considered secure against well-funded opponents; as of 2010 many organizations have recommended its replacement. NIST formally deprecated use of SHA-1 in 2011 and disallowed its use for digital signatures in 2013, and declared that it should be phased out by 2030. , chosen-prefix attacks against SHA-1 are practical. As such, it is recommended to remove SHA-1 from products as soon as possible and instead use SHA-2 or SHA-3. Replacing SHA-1 is urgent where it is used for digital signatures. All major web browser vendors ceased acceptance of SHA-1 SSL certificates in 2017. In February ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Tape
Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnetic tape could with relative ease record and playback audio, visual, and binary computer data. Magnetic tape revolutionized sound recording and reproduction and broadcasting. It allowed radio, which had always been broadcast live, to be recorded for later or repeated airing. Since the early 1950s, magnetic tape has been used with computers to store large quantities of data and is still used for backup purposes. Magnetic tape begins to degrade after 10–20 years and therefore is not an ideal medium for long-term archival storage. Durability While good for short-term use, magnetic tape is highly prone to disintegration. Depending on the environment, this process may begin after 10–20 years. Over time, magnetic tape made in the 197 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Remote Procedure Call
In distributed computing, a remote procedure call (RPC) is when a computer program causes a procedure (subroutine) to execute in a different address space (commonly on another computer on a shared network), which is coded as if it were a normal (local) procedure call, without the programmer explicitly coding the details for the remote interaction. That is, the programmer writes essentially the same code whether the subroutine is local to the executing program, or remote. This is a form of client–server interaction (caller is client, executor is server), typically implemented via a request–response message-passing system. In the object-oriented programming paradigm, RPCs are represented by remote method invocation (RMI). The RPC model implies a level of location transparency, namely that calling procedures are largely the same whether they are local or remote, but usually, they are not identical, so local calls can be distinguished from remote calls. Remote calls are usually orde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bucket (computing)
In computing, the term bucket can have several meanings. It is used both as a live metaphor, and as a generally accepted technical term in some specialised areas. A bucket is most commonly a type of data buffer or a type of document in which data is divided into regions. Features of a bucket Various usages relate to different features. There is no usage that is consistent with every one of these features. *The contents of a bucket are unsorted. *A bucket has a fixed size, which is determined when it is created. *A bucket has a limited number of states: **It may be empty. **It may be non-empty. Some usages further distinguish: ***It may be partly full. ***It may be full. Some usages further distinguish: ****It may be exactly full. ****It may be overflowing. Types of bucket Bit bucket This is a humorous but common phrase. Something goes into the bit bucket In computing jargon, the bit bucket (or byte bucket) is where lost computerized data has gone, by any means; any data wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
