EMC MirrorView provides highly available data storage across rooms, across buildings or across the globe. By maintaining synchronous or asynchronous data mirroring between EMC CX arrays, MirrorView helps ensure data availability for important business functions. MirrorView is an array based application, minimizing the impact to your server while maximizing data uptime. MirrorView also integrates with EMC SnapView point-in-time snapshot software. Together, MirrorView and SnapView provide a unique solution for online data availability and disaster recovery.
MirrorView is easily configured and managed from within EMC’s Navisphere management software. In a MirrorView/Synchronous (MirrorView/S) configuration, a server writes to the source array, which records the data and synchronously writes the same data to the target array. An acknowledgement is sent back to the server once the data has been written to both the source and target arrays, ensuring a complete transaction record on both arrays. In a MirrorView/Asynchronous (MirrorView/A) configuration, a server writes to the source array, which immediately acknowledges the write. The data can then be written to the target array in the background, decreasing the original write time and eliminating the distance requirements of MirrorView/S.
Data is protected throughout the entire mirroring process. Fracture logs track changes and provide a source for restoring modifications to source data in the event that the source array loses contact with the target array during a failure. When the target array returns to availability, the pending writes in the fracture log are written to the target array restoring its consistent state. A write-intent log is also kept in the unlikely event of a source array issue. Upon repair of a source array, MirrorView/S will access the write intent log to make any changes that were in process between the two arrays during the failure, to the source data. Then, a partial re-sync with the target array can take place to return to a consistent state between the source and target arrays.
MirrorView/A provides the ability to mirror data over long distances and help reduce network costs. Its ability to help reduce bandwidth requirements and minimize data exposure lies in the Delta Set architecture. MirrorView/A Delta Sets are disk-resident collections of writes that have occurred within a specific period of time. In addition to providing consistent restartable images at the target site, Delta Sets reduce the bandwidth needed between sites in two ways. First, if the same data is overwritten several times within a Delta Set, only the latest version of data is sent. Second is the ability to size your communication links to your average write workload rather than your peak workload. MirrorView/A also supports the array level Consistency Group feature. Remote data replication and system-based software MirrorView operates on the array. By off-loading the mirroring process from the server to the array, the server is free to service application I/Os, instead of managing the data replication process. Because the arrays are redundant, MirrorView operation is protected from a server failure.