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Shardmap
Shardmap is a directory index design by Daniel Phillips who created the HTree and PHTree tree data structures and the Tux3 file system. A Shardmap index consists of a scalable number of index shards. Each shard entry maps a hash key to the logical block number of a directory entry block known to contain a name that hashes to that key. Each shard is represented as an unsorted fifo on disk and a small hash table in memory. Shardmap scales in two ways: # Rehash a cached shard to a larger number of hash buckets # Reshard a stored shard fifo to divide it into multiple, smaller shards. These operations are staggered to avoid latency spikes. The reshard operation imposes a modest degree of write multiplication on the Shardmap design, asymptotically approaching a factor of two. The key ideas of Shardmap are: # The representation of directory data is not the same on media as it is in cache. On media we have fifos, but in cache we have hash tables. # Updating a fifo is cache efficient. On ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tux3
Tux3 is an open-source versioning filesystem created by Daniel Phillips. He introduced the filesystem as a public replacement for his Tux2 filesystem which had encountered licensing issues due to the filing of several patents. Phillips had previously created the Htree directory indexing system which eventually became an official feature of ext3. The technical details of Tux3 were first publicized in an email on 23 July 2008. Design In broad outline, Tux3 follows a conventional Unix-style inode/file/directory design. A Tux3 inode table is a B-tree with versioned attributes at the leaves. A file is an inode attribute that is a B-tree with versioned Extent (file systems), extents at the leaves. Directory indexes are mapped into directory file blocks as with Htree. Free space is mapped by a B-tree with extents at the leaves. It attempts to avoid traditional journaling file system, journaling by introducing a recovery logic which allows it to recover upon remounting. A Tux3 inode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash Table
In computer science, a hash table is a data structure that implements an associative array, also called a dictionary or simply map; an associative array is an abstract data type that maps Unique key, keys to Value (computer science), values. A hash table uses a hash function to compute an ''index'', also called a ''hash code'', into an array of ''buckets'' or ''slots'', from which the desired value can be found. During lookup, the key is hashed and the resulting hash indicates where the corresponding value is stored. A map implemented by a hash table is called a hash map. Most hash table designs employ an Perfect hash function, imperfect hash function. Hash collision, Hash collisions, where the hash function generates the same index for more than one key, therefore typically must be accommodated in some way. In a well-dimensioned hash table, the average time complexity for each lookup is independent of the number of elements stored in the table. Many hash table designs also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SipHash
SipHash is an add–rotate–xor (ARX) based family of pseudorandom functions created by Jean-Philippe Aumasson and Daniel J. Bernstein in 2012, in response to a spate of "hash flooding" denial-of-service attacks (HashDoS) in late 2011. SipHash is designed as a secure pseudorandom function and can also be used as a secure message authentication code (MAC). SipHash, however, is not a general purpose key-less hash function such as Secure Hash Algorithms (SHA) and therefore must always be used with a secret key in order to be secure. That is, SHA is designed so that it is difficult for an attacker to find two messages ''X'' and ''Y'' such that SHA(''X'') = SHA(''Y''), even though anyone may compute SHA(''X''). SipHash instead guarantees that, having seen ''Xi'' and SipHash(''Xi'', ''k''), an attacker who does not know the key ''k'' cannot find (any information about) ''k'' or SipHash(''Y'', ''k'') for any message ''Y'' ∉ which they have not seen before. Overview SipHash comput ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Daniel J
Daniel commonly refers to: * Daniel (given name), a masculine given name and a surname * List of people named Daniel * List of people with surname Daniel * Daniel (biblical figure) * Book of Daniel, a biblical apocalypse, "an account of the activities and visions of Daniel" Daniel may also refer to: Arts and entertainment Literature * ''Daniel'' (Old English poem), an adaptation of the Book of Daniel * ''Daniel'', a 2006 novel by Richard Adams * ''Daniel'' (Mankell novel), 2007 Music * "Daniel" (Bat for Lashes song) (2009) * "Daniel" (Elton John song) (1973) * "Daniel", a song from '' Beautiful Creature'' by Juliana Hatfield * ''Daniel'' (album), a 2024 album by Real Estate Other arts and entertainment * ''Daniel'' (1983 film), by Sidney Lumet * ''Daniel'' (2019 film), a Danish film * Daniel (comics), a character in the ''Endless'' series Businesses * Daniel (department store), in the United Kingdom * H & R Daniel, a producer of English porcelain between 1827 and 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dirhash
Dirhash is a feature of FreeBSD that improves the speed of finding files in a directory. Rather than finding a file in a directory using a linear search algorithm, FreeBSD uses a hash table. The feature is backwards-compatible because the hash table is built in memory when the directory is accessed, and it does not affect the on-disk format of the filesystem, in contrast to systems such as Htree. Free space for new entries is also tracked in-memory, allowing addition of new entries without having to scan the directory. Dirhash was implemented by Ian Dowse early in 2001 as an addition to UFS, operating in parallel with higher-level file system caching. It was imported into FreeBSD in July 2001. It was subsequently imported into OpenBSD in December 2003 and 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 developmen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux Kernel Mailing List
The Linux kernel mailing list (LKML) is the main electronic mailing list for Linux kernel development, where the majority of the announcements, discussions, debates, and flame wars over the kernel take place. Many other mailing lists exist to discuss the different subsystems and ports of the Linux kernel, but LKML is the principal communication channel among Linux kernel developers. It is a very high-volume list, usually receiving about 1,000 messages each day, most of which are kernel code patches. Linux utilizes a workflow governed by LKML, which is the "bazaar" where kernel development takes place. In his book ''Linux Kernel Development'', Robert Love notes: The LKML functions as the central place where Linux developers around the world share patches, argue about implementation details, and discuss other issues. The official releases of the Linux kernel are indicated by an email to LKML. New features are discussed and most code is posted to the list before any action is t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
