by Angela Guess
Ilya Katsov recently wrote, “Scalability is one of the main drivers of the NoSQL movement. As such, it encompasses distributed system coordination, failover, resource management and many other capabilities. It sounds like a big umbrella, and it is. Although it can hardly be said that NoSQL movement brought fundamentally new techniques into distributed data processing, it triggered an avalanche of practical studies and real-life trials of different combinations of protocols and algorithms. These developments gradually highlight a system of relevant database building blocks with proven practical efficiency. In this article I’m trying to provide more or less systematic description of techniques related to distributed operations in NoSQL databases.”
Katsov goes on, “It is well known and fairly obvious that in geographically distributed systems or other environments with probable network partitions or delays it is not generally possible to maintain high availability without sacrificing consistency because isolated parts of the database have to operate independently in case of network partition. This fact is often referred to as the CAP theorem. However, consistency is a very expensive thing in distributed systems, so it can be traded not only to availability. It is often involved into multiple tradeoffs.”
