Home | Contents | Help   Raidhelp     Defining RAID Level 1 (Disk Mirroring) RAID Level 1 also known as Mirroring, has been used longer than any other RAID Level and remains popular because of its simplicity and high levels of reliability and availability. Mirroring consists of a minimum of two physical disk drives, or multiples of drive pairs. Each pair of physical disks stores an identical set of all data transferred to the controller, one data set on each disk. RAID Level 1 may use parallel access for high transfer rates, or more commonly, independent access for high transaction rates. RAID Level 1 provides very high data reliability and improved performance for read-intensive applications, but at a relatively high inherent cost. It literally retains a mirrored image of your drive on an identical drive, essentially doubling the hardware requirements. RAID 1 has the highest ECC (Error Checking/Correction) disk overhead of all RAID variants - 100%. This inefficiency is usually taken on by the CPU of the host if an independent hardware controller is not used, causing possible degradation of throughput at high activity levels. In summary, Level 1 is the simplest to implement, offers the highest data protection, and is the costliest to build. Next: Level 1 - Duplexing Related topics: Defining RAID Levels Level 1/0: Combined Mirroring/Striping   Raidhelp   RAIDhelp© Copyright 1999-2004 Antony Kershaw