HP Xw6200 Software RAID in Linux Workstations - Page 7

Additional RAID Levels More RAID levels can be created from the basic RAID levels by means of nesting. This is accomplished by creating a second RAID array of other RAID disks, instead of creating a RAID of physical disks. Nested RAID levels include RAID-0+1, a mirrored array of striped disks, RAID-10 (RAID-1+0), a striped array of mirrored disks, RAID-100 (RAID-10+0), which is a striped array of RAID-10 arrays, RAID-5+0, RAID-0+5, and other combinations. In nested RAID solutions, it is preferable to have a RAID-0 level on top to provide better performance as well as reducing the number of disks that need to be regenerated when a disk fails. For example, RAID-10 is usually preferred over RAID-0+1. Nested RAID levels are not supported by the Red Hat Enterprise Linux installer, and must be configured manually. Software RAID-10 is the only additional RAID level supported by HP Linux workstations. Please note that while the Linux kernel allows for RAID-linear, -0, -1, -4, -5, and nested RAID levels, HP only provides support for RAID-0, 1, 5, and 10. RAID Configuration Strategies Configuration of RAID workstations must take several factors into account in order to deliver optimal performance, capacity, and redundancy. Note that the cost to implement RAID solutions increases as desired performance, capacity, and redundancy increases. Users should consider the following when designing an ideal RAID workstation: Performance Multiple factors must be taken into account, including both random and sequential read and write speeds, latency times, and bus types; CPU and RAM configurations play a heavy part in the performance of a software RAID solution as well. Such technical details are beyond the scope of this document. Capacity versus Fault-Tolerance With most implementations of RAID, capacity and fault-tolerance are mutually exclusive. Cost Obviously, as the number of physical disks required for an installation increases, the cost also increases. 7