|
Rendezvous Hashing
Rendezvous or highest random weight (HRW) hashing is an algorithm that allows clients to achieve distributed agreement on a set of k options out of a possible set of n options. A typical application is when clients need to agree on which sites (or proxies) objects are assigned to. Consistent hashing addresses the special case k = 1, using a different method. Rendezvous hashing is both much simpler and more general than consistent hashing (see below). History Rendezvous hashing was invented by David Thaler and Chinya Ravishankar at the University of Michigan in 1996. Consistent hashing appeared a year later in the literature. Given its simplicity and generality, rendezvous hashing is now being preferred to consistent hashing in real-world applications. Rendezvous hashing was used very early on in many applications including mobile caching, router design, secure key establishment, and sharding and distributed databases. Other examples of real-world systems that use Rendezvous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Load Balancing (computing)
In computing, load balancing is the process of distributing a set of tasks over a set of resources (computing units), with the aim of making their overall processing more efficient. Load balancing can optimize the response time and avoid unevenly overloading some compute nodes while other compute nodes are left idle. Load balancing is the subject of research in the field of parallel computers. Two main approaches exist: static algorithms, which do not take into account the state of the different machines, and dynamic algorithms, which are usually more general and more efficient but require exchanges of information between the different computing units, at the risk of a loss of efficiency. Problem overview A load-balancing algorithm always tries to answer a specific problem. Among other things, the nature of the tasks, the algorithmic complexity, the hardware architecture on which the algorithms will run as well as required error tolerance, must be taken into account. Therefore c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash Function
A hash function is any function that can be used to map data of arbitrary size to fixed-size values. The values returned by a hash function are called ''hash values'', ''hash codes'', ''digests'', or simply ''hashes''. The values are usually used to index a fixed-size table called a ''hash table''. Use of a hash function to index a hash table is called ''hashing'' or ''scatter storage addressing''. Hash functions and their associated hash tables are used in data storage and retrieval applications to access data in a small and nearly constant time per retrieval. They require an amount of storage space only fractionally greater than the total space required for the data or records themselves. Hashing is a computationally and storage space-efficient form of data access that avoids the non-constant access time of ordered and unordered lists and structured trees, and the often exponential storage requirements of direct access of state spaces of large or variable-length keys. Use of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM Cloud Object Storage
IBM Cloud Object Storage is a service offered by IBM for storing and accessing unstructured data. The object storage service can be deployed on-premise, as part of IBM Cloud Platform offerings, or in hybrid form. The offering can store any type of object which allows for uses like data archiving and backup, web and mobile applications, and as scalable, persistent storage for analytics. Interaction with Cloud Object Storage is based on Rest APIs. Design IBM Cloud Object Storage stores objects that are organized into buckets (as S3 does) identified within each bucket by a unique, user-assigned key. All requests are authorized using an access control list associated with each bucket and object. Bucket names and keys are chosen so that objects are addressable using HTTP URLs. Features IBM Cloud Object Storage offers different storage classes, identical in data protection, security, durability and resiliency. The classes differ in data pattern and availability needs. History The o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cleversafe
IBM Cloud Object Storage is a service offered by IBM for storing and accessing unstructured data. The object storage service can be deployed on-premise, as part of IBM Cloud Platform offerings, or in hybrid form. The offering can store any type of object which allows for uses like data archiving and backup, web and mobile applications, and as scalable, persistent storage for analytics. Interaction with Cloud Object Storage is based on Rest APIs. Design IBM Cloud Object Storage stores objects that are organized into buckets (as S3 does) identified within each bucket by a unique, user-assigned key. All requests are authorized using an access control list associated with each bucket and object. Bucket names and keys are chosen so that objects are addressable using HTTP URLs. Features IBM Cloud Object Storage offers different storage classes, identical in data protection, security, durability and resiliency. The classes differ in data pattern and availability needs. History The o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hrw Skeleton
Human Rights Watch (HRW) is an international non-governmental organization, headquartered in New York City, that conducts research and advocacy on human rights. The group pressures governments, policy makers, companies, and individual human rights abusers to denounce abuse and respect human rights, and the group often works on behalf of refugees, children, migrants, and political prisoners. Human Rights Watch, in 1997, shared the Nobel Peace Prize as a founding member of the International Campaign to Ban Landmines, and it played a leading role in the 2008 treaty banning cluster munitions. The organization's annual expenses totaled $50.6 million in 2011, $69.2 million in 2014, and $75.5 million in 2017. History Human Rights Watch was co-founded by Robert L. Bernstein Jeri Laber and Aryeh Neier as a private American NGO in 1978, under the name Helsinki Watch, to monitor the then-Soviet Union's compliance with the Helsinki Accords. Helsinki Watch adopted a practice of publicl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ceph (software)
Ceph (pronounced ) is an open-source software-defined storage platform that implements object storage on a single distributed computer cluster and provides 3-in-1 interfaces for object-, block- and file-level storage. Ceph aims primarily for completely distributed operation without a single point of failure, scalability to the exabyte level, and to be freely available. Since version 12, Ceph does not rely on other filesystems and can directly manage HDDs and SSDs with its own storage backend BlueStore and can completely self reliantly expose a POSIX filesystem. Ceph replicates data and makes it fault-tolerant, using commodity hardware and Ethernet IP and requiring no specific hardware support. The Ceph’s system offers disaster recovery and data redundancy through techniques such as replication, erasure coding, snapshots and storage cloning. As a result of its design, the system is both self-healing and self-managing, aiming to minimize administration time and other co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reduction (complexity)
In computability theory and computational complexity theory, a reduction is an algorithm for transforming one problem into another problem. A sufficiently efficient reduction from one problem to another may be used to show that the second problem is at least as difficult as the first. Intuitively, problem ''A'' is reducible to problem ''B'', if an algorithm for solving problem ''B'' efficiently (if it existed) could also be used as a subroutine to solve problem ''A'' efficiently. When this is true, solving ''A'' cannot be harder than solving ''B''. "Harder" means having a higher estimate of the required computational resources in a given context (e.g., higher time complexity, greater memory requirement, expensive need for extra hardware processor cores for a parallel solution compared to a single-threaded solution, etc.). The existence of a reduction from ''A'' to ''B'', can be written in the shorthand notation ''A'' ≤m ''B'', usually with a subscript on the ≤ to indicate the t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamo (storage System)
Dynamo is a set of techniques that together can form a highly available key-value structured storage system or a distributed data store. It has properties of both databases and distributed hash tables (DHTs). It was created to help address some scalability issues that Amazon.com's website experienced during the holiday season of 2004. By 2007, it was used in Amazon Web Services, such as its Simple Storage Service (S3). Relationship to DynamoDB Amazon DynamoDB is "built on the principles of Dynamo" and is a hosted service within the AWS infrastructure. However, while Dynamo is based on leaderless replication, DynamoDB uses single-leader replication. Principles * Incremental scalability: Dynamo should be able to scale out one storage host (or “node”) at a time, with minimal impact on both operators of the system and the system itself. * Symmetry: Every node in Dynamo should have the same set of responsibilities as its peers; there should be no distinguished node or nod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hit Rate
Hit rate is a metric or measure of business performance traditionally associated with sales. It is defined as the number of sales of a product divided by the number of customers who go online, planned call, or visit a company to find out about the product. Sales can be measured either as the sum of dollars pursued or the number of deals pursued. Accurate calculation requires clear definition of when a sales opportunity is firm enough to be included in the metric, as well as firm disposition of the opportunity (i.e. the deal has reached a point where it is considered won, lost or abandoned). The hit rate may be measured for the whole sales force or by sales region, sales person or product group. It may be used to benchmark the different sales periods and to benchmark the effectiveness of the own sales force with other companies of the same sector. Due to the high costs involved with making proposals, the hit rate is a very useful tool especially for companies in industrial market ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash Table
In computing, a hash table, also known as hash map, is a data structure that implements an associative array or dictionary. It is an abstract data type that maps keys to 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. Ideally, the hash function will assign each key to a unique bucket, but most hash table designs employ an imperfect hash function, which might cause hash ''collisions'' where the hash function generates the same index for more than one key. Such collisions are typically 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 allow arbitrary insertions and deletions of key–value pairs, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Consistent Hashing
In computer science, consistent hashing is a special kind of hashing technique such that when a hash table is resized, only n/m keys need to be remapped on average where n is the number of keys and m is the number of slots. In contrast, in most traditional hash tables, a change in the number of array slots causes nearly all keys to be remapped because the mapping between the keys and the slots is defined by a modular operation. History The term "consistent hashing" was introduced by David Karger ''et al.'' at MIT for use in distributed caching, particularly for the web. This academic paper from 1997 in Symposium on Theory of Computing introduced the term "consistent hashing" as a way of distributing requests among a changing population of web servers. Each slot is then represented by a server in a distributed system or cluster. The addition of a server and the removal of a server (during scalability or outage) requires only num\_keys/num\_slots items to be re-shuffled when the nu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
