Otherwise a single point of failure would still exist. Mirrored disks are designed to provide high data availability by automatically maintaining identical information on two partner disks. When an application writes to a disk, disk mirroring causes the information to be written to both drive partners. When an application reads from a disk, there are two places to access the requested data. This may give performance benefits on large systems which do a lot of reads for queries but only a few writes to the same data.
Applications running on the system are unaware that disk mirroring is present.
If either disk of any pair fails, normal system operation continues. When the partner is ready to resume operation, the system copies data from the good disk, bringing the pair to a consistent state, and normal mirroring resumes. Once mirrored disks have been installed, you can use them like any other disks connected to the system. Additionally, you can perform split-volume backup of mirrored disk data while still accessing the data. Users continue to access data if either disk of any pair is disabled or under repair.