Disk Mirroring

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In the context of storage of data, disk mirroring is referred to as the cloning of logical disk volumes onto different physical hard disks in real time to ascertain unceasing accessibility. It is usually used in RAID 1. A replicated volume is an in-depth and coherent representation of distinct volume copies.


While in events of Disaster Recovery, mirroring of data over long distance is denoted as storage duplication. The replication of the data can be performed in a synchronous, asynchronous, semi-synchronous manner, or point-in-time, but the complete process totally depends on the technology used. Replication is facilitated either through microcode on the disk array controller or server software. It provides high accessibility of data simply by diminishing the downtime to a great extent that can happen due to unexpected failure of physical disk.


There are two types of mirroring: synchronous and asynchronous


In the Synchronous Mirroring provision, every time data is copied to a selected disk and concurrently same data is also copied to another disk. This way, the disk always upholds a duplicate copy of the primary disk.


In an asynchronous mirroring provision, you create a dedicated cache resource and connect it to a managed disk. Once the copy is generated, the primary and secondary disks are orchestrated and the whole process doesn’t even require any application server. After the orchestration is over, all write-requests from the connected application server are chronologically delivered to the dedicated cache resource.




Reference

1. Disk mirroring - Wikipedia, the free encyclopedia
2. What's the difference between Asynchronous and Synchronous Mirrors?