IBM 86624RY Maintenance Manual - Page 76

The ServeRAID adapters and controllers support RAID level-0, RAID level-1, Enhanced RAID level-1, and RAID level-5. RAID level-0: RAID level-0 stripes the data across all the drives in the array. This offers substantial speed enhancement, but provides for no data redundancy. RAID level-0 provides the largest capacity of the RAID levels offered, because no room is taken up for redundant data or data-parity storage. The following illustration shows data arranged in an array of three hard disk drives defined as one RAID level-0 logical drive. Notice that the data is striped across all the drives in the array, but no copies of the data or parity information is stored. Stripe 1 Stripe 2 Stripe 3 . . Block 1 Block 4 Block 7 . . Block 2 Block 5 Block 8 . . Block 3 Block 6 Block 9 A hard disk failure within the array results in loss of data in the logical drive assigned RAID level-0, but only in that logical drive. If there are logical drives assigned RAID level-1 or level-5 in the same array, they will not lose data. Note The ServeRAID controller automatically assigns RAID level-0 to all logical drives in an array containing only one hard disk drive. When you replace a failed drive, the ServeRAID controller can rebuild all the RAID level-1 and RAID level-5 logical drives automatically onto the replacement hard disk drive. However, any data stored in a failed RAID level-0 logical drive is lost. Though the risk of data loss is present, you might want to assign RAID level-0 to one of the logical drives to take advantage of the speed offered with this RAID level. You could use this logical drive to enter data that is backed up each day and for which safety is not of primary importance, that is, data that can be easily re-created. You also might want to use a RAID level-0 logical drive when the work being done requires maximum capacity. 68 Netfinity Server HMM