Microsoft® SQL Server 2012 Unleashed

RAID Level 1

With RAID 1, known as disk mirroring, every write to the primary disk is written to the mirror set. Either member of the set can satisfy a read request. RAID 1 devices provide excellent fault tolerance because in the event of a media failure, either on the primary disk or mirrored disk, the system can still continue to run. Writes are much faster than with RAID 5 arrays because no parity information needs to be calculated first. The data is simply written twice.

RAID 1 arrays are best for transaction logs and index filegroups. RAID 1 provides the best fault tolerance and best write performance, which is critical to log and index performance. Because log writes are sequential write operations and not random access operations, they ...