It provides protect against data loss due to power outages. Two or more drives work in tandem to provide redundant data storage. RAID-1 is a mirroring process at the sector level or lower, with a single controllerboard managing multiple hard drives in most implementations. Data bytes are stripped and spread among the drives, but without an advanced error-checking protocol. RAID-2 is a duplexing setup.
Parity codes provide error detection and correction.
RAID-2 is fast for large file transfers, but less efficient for small file transfers, because all drives in the array are accessed for every request. Drive thoughput, for any manufacturer's implementation of a RAID is also determined by the application, block size of the data transfers, and operating system. Data is transferred in parallel to data and parity drives. The parity drive stores a complementary copy of the parity information When a data drive fails, the remaining data drives and the parity drive together can recreate the missing information. Access time is determined by the number of drives in the array.