Level 0: Often called "striping," is a performance-oriented data mapping technique. Data written to the array are divided into stripes and written across the disks of the array. This procedure enables high I/O performance at a low cost but provides no redundancy.
Level 1: Often called "mirroring," provides redundancy by writing identical data to each member disk of the array. Level 1 operates with two disks that may use parallel access for high data-transfer rates when reading, but more commonly operates independently to provide high I/O transaction rates. Level 1 provides very good data reliability and improves performance for read-intensive applications but at a relatively high cost. Minimum number of drives is two.
Level 5: RAID Level 5 is the most common type of RAID. By distributing parity across some or all of an array's member disk drives, RAID level 5 eliminates the write bottleneck inherent in level 4. As with level 4, the result is asymmetrical performance, with reads substantially outperforming writes. Level 5 is often used with write-back caching to reduce the asymmetry. Because parity data must be skipped on each drive during reads, however, the performance for reads tends to be considerably lower than a level 4 array. Minimum number of drives is three.
Level 10: RAID level 10 employs the features of levels 1 and 0. The advantages are faster data access (like RAID 0), and single-drive fault tolerance (like RAID 1). RAID 10 requires twice the number of disks (like RAID 1), but it offers some performance improvements by striping, then mirroring the striped array. RAID 10 stripes the blocks of data to each RAID 1 array. Each RAID 1 array then duplicates its data to its other drive. Minimum number of drives is four.
Level 50: RAID level 50 employs the features of levels 5 and 0. RAID 50 includes both parity and disk striping across multiple drive groups. RAID 50 is best implemented on two RAID 5 disk arrays with data striped across both arrays. RAID 50 can sustain one to four drive failures while maintaining data integrity if each failed disk is in a different RAID 5 array. Minimum number of drives is six.
This applies to: