Cloud Basics - Availability and Redundancy
High Availability Your ability for your service to remain available by ensuring there is *no single point Of failure and/or ensure a certain level of performance. High availability is achieved by replicating the images in multiple zones or data centres. So in case of any geo-disaster the alternative systems serve the users, hence it is called highly available. There are three types of redundancies: Local Redundancy Zone Redundancy Global/Geo Redundancy Local redundancy The default behaviour is locally replicating the data/resource images in multiple copies in the same datacentre. The resources by default have three copies. so if one copy fail to serve the other two are still available. This mode has less availability comparing to the other two but still it provides some piece of mind. Zones Redundancy In this mode three copies of the resources are kept in three different zones or data centres in the same location/city. For example, UK West is a location which may...