IBM 866011U Hardware Maintenance Manual - Page 91

The Enhanced RAID level 1 stripes data and copies of the data across all the drives in the array. As with the standard RAID level 1, the data is mirrored, and the capacity of the logical drive is 50% of the physical capacity of the grouping of hard disk drives in the array. The following illustration shows data arranged in an array with three hard disk drives. The logical drive is assigned the Enhanced level 1. Notice that the mirror of the first data stripe (XXX YYY ZZZ) is shifted one drive. The other data stripes in level 1 follow the same pattern. . . . . . . Stripe XXX YYY ZZZ Mirrored stripe ZZZ XXX YYY Stripe AAA BBB CCC Mirrored stripe CCC AAA BBB Table 1. Enhanced RAID Level 1 If you have only two drives available, the second drive is a mirror copy of the first drive. RAID level 5: RAID level 5 stripes data and parity across all drives in the array. When an array is assigned level 5, the capacity of the logical drive is reduced by one drive (for data parity storage). RAID level 5 is generally the most desirable choice, because it offers both data protection and increased throughput. RAID level 5 gives you higher capacity than level 1, but level 1 offers better performance. If you want to have a hot-spare drive (that is, a drive that can be automatically used to replace a similar drive that fails) and also assign RAID level 5, you must have at least four hard disk drives in the server. ServeRAID menus, screens, and drive states: The following information describes the Main Menu, the ServeRAID screens and pop-up windows, the physical device states, and the logical drive states. Netfinity 5500 - Type 8660 83