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Movements, leaders, victories and the continuing fight for equality.
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Mansa Musa was the ruler of the Mali Empire in West Africa. Details recorded here should be sourced; unknown information is left blank.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
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Dynamo is a set of techniques that together can form a highly available key-value structured storage system[1] or a distributed data store.[1] It has properties of both databases and distributed hash tables (DHTs). It was created to help address some scalability issues that Amazon experienced during the holiday season of 2004.[2] By 2007, it was used in Amazon Web Services, such as its Simple Storage Service (S3).[1]
Amazon DynamoDB is "built on the principles of Dynamo"[3] and is a hosted service within the AWS infrastructure. However, while Dynamo is based on leaderless replication, DynamoDB uses single-leader replication.[4]
| Problem | Technique | Advantage |
|---|---|---|
| Dataset partitioning | Consistent Hashing | Incremental, possibly linear scalability in proportion to the number of collaborating nodes. |
| Highly available writes | Vector Clock or Dotted-Version-Vector Sets, reconciliation during reads | Version size is decoupled from update rates. |
| Handling temporary failures | Sloppy Quorum and Hinted Handoff | Provides high availability and durability guarantee when some of the replicas are not available. |
| Recovering from permanent failures | Anti-entropy using Merkle tree | Can be used to identify differences between replica owners and synchronize divergent replicas pro-actively. |
| Membership and failure detection | Gossip-based membership protocol and failure detection | Avoids having a centralized registry for storing membership and node liveness information, preserving symmetry. |
Amazon published the paper on Dynamo, but never released its implementation. The index layer of Amazon S3 implements and extends many core features of Dynamo. Since then, several implementations have been created based on the paper. The paper also inspired many other NoSQL database implementations, such as Apache Cassandra, Project Voldemort and Riak.[2]
Dynamo is not available to users outside of Amazon. Confusingly, AWS offers a hosted database product called DynamoDB, which uses a completely different architecture: it is based on single-leader replication.
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
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 experienced during the holiday season of 2004. By 2007, it was used in Amazon Web Services, such as its Simple Storage Service (S3).
Apache Cassandra is a free and open-source database management system designed to handle large volumes of data across multiple commodity servers. The system prioritizes availability and scalability over consistency, making it particularly suited for systems with high write throughput requirements due to its LSM tree indexing storage layer. As a wide-column database, Cassandra supports flexible schemas and efficiently handles data models with numerous sparse columns. The system is optimized for applications with well-defined data access patterns that can be incorporated into the schema design. Cassandra supports computer clusters which may span multiple data centers, featuring asynchronous and masterless replication. It enables low-latency operations for all clients and incorporates Amazon's Dynamo distributed storage and replication techniques, combined with Google's Bigtable data storage engine model.
Amazon Elastic File System (Amazon EFS) is a cloud storage service provided by Amazon Web Services (AWS) designed to provide scalable, elastic, concurrent with some restrictions, and encrypted file storage for use with both AWS cloud services and on-premises resources. Amazon EFS is built to be able to grow and shrink automatically as files are added and removed. Amazon EFS supports Network File System (NFS) versions 4.0 and 4.1 (NFSv4) protocol, and control access to files through Portable Operating System Interface (POSIX) permissions.
Hybrid power are combinations between different technologies to produce power. In power engineering, the term 'hybrid' describes a combined power and energy storage system. Examples of power producers used in hybrid power are photovoltaics, wind turbines, and various types of engine-generators – e.g., diesel gen-sets. Hybrid power plants often contain a renewable energy component (such as PV) that is balanced via a second form of generation or storage such as a diesel genset, fuel cell or battery storage system. They can also provide other forms of power such as heat for some applications.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →The Greenwood District.
