RAID Level 10 (1+0) requires a minimum of 4 drives to implement. A RAID 10 is a striped array with segments consisting of RAID 1 arrays and having the same fault tolerance as RAID level 1 plus the overhead fault-tolerance of mirroring. In certain instances a RAID 10 array can recover from multiple and simultaneous hard drive failure. Because of limited scalability and high inherent costs, RAID 1+0 is typically used in database server applications like an Exchange Server or SQL database server which requires high performance and high fault tolerance levels.
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