The method in which stored data is copied from one storage array to another
Can happen locally over a SAN or LAN or even to remote locations over a WAN
Deals with duplicating archived data. Also called file replication, data replication, and remote storage replication.
Advantages of Storage Replication
Improves reliability, fault tolerance, performance, and accessibility of data
Remote users can access data that is replicated to remote locations
Allows resources, information, software, and hardware to be shared with multiple systems
Different Types of Storage Replication
• Point-in-Time Replication
• Continuous Replication
• Synchronous Replication
• Asynchronous Replication
• Remote Replication
Point-in-Time Replication
• Point-In-Time (PPT) replication is one that is matching to the source per a precise time and date
• Tracks change between the source and PIT replication so that synchronization may happen
• Bitmaps are used. Bitmaps reference each block on the source volume to a bit within the bitmap.
Continuous Replication
• Synchronized with the source at continuous repeating intervals
• Can be asynchronous and synchronous
Synchronous Replication
• Doesn’t finalize transactions or commit data until it has been written to destination and source
• Makes sure all data remains consistent in both sites
• Expensive and slows down the speed of the primary system
• Either write data in both primary and secondary data drives or not at all
• Asynchronous Replication
• Data is written to the primary first, then the secondary system
• Better performance than synchronous replication, however prevention of data loss is not guaranteed
• Buffer size impacts consistency
• Remote Replication
• Replication that occurs to another site
• Must take latency and bandwidth into account
• Can happen via disk-buffered replication, storage array remote replication, or log shipping
• Why Storage Replication is Necessary
• Site Redundancy- a technique where a full duplicate of data present in computers in one location is replicated at a different location
• Both sites’ data is duplicated so in the event of a failure, data can be quickly restored
• Software upgrades are also enhanced since they can be performed at one site and not interfere with normal operations at the other site
• Replication Consistency
• Gained through consistency groups that are used for maintaining the integrity of data and uniformity across multiple volumes and sites
• Comprises whole systems such as middleware, application, and backend
• Makes sure no matter which resource is accessed, data remains the same
• References
• Vanderburg, Eric. (2015). CompTIA Storage+ Quick Review Guide. McGraw Hill Education.
• Rouse, Margaret. (n.d.). Storage Replication. Retrieved from http://searchstorage.techtarget.com/definition/storage-replication-service.
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