Understanding RAID arrays
Redundant Arrays of Independent Disks (RAID) technology allows a computer to use two or more hard disks at the same time. RAID treats multiple drives as one contiguous drive, either through hardware or software settings. If multiple disks are set up to work together in this fashion, they are referred to as a RAID array .
Users should consider the advantages and the restrictions before trying to setup a RAID array. If the PC was not manufactured and configured with RAID, it may be necessary to purchase a separate operating system or license, and reformat the drives before configuring the arrays. Keep in mind that the new operating system you purchase must be supported by the hardware and component manufactures to ensure that model specific firmware and drivers are available. Also, depending on the RAID array, it may be necessary to use a separate data backup system.
What benefits does a RAID array offer?
The computer sees multiple disks in a RAID array as one contiguous hard drive, with the goal of providing better data reliability or faster performance.
Some RAID arrays provide backup redundancy for data by organizing data in files across multiple physical hard disks. With this configuration, if one physical disk fails, some of the data can be reconstructed. Other RAID array configurations provide more speed and data efficiency in storing data, but do not offer data redundancy.
NOTE:A RAID array configured for file redundancy is not a substitute for proper file backups. Data can become corrupted or overwritten even if the physical hard disk itself is undamaged.
What are the different types of RAID arrays?
RAID technology allows improvements in data redundancy and speed. For sophisticated or complex situation, there are six RAID configurations. However this document only addresses three of the most common configurations.
- RAID 1 - Mirroring. In mirroring, the same data is copied to more than one physical disk. This mirrored array provides some file redundancy, however this can reduce the amount of space that is actually usable on the hard drives. With mirroring, the data is probably recoverable even if one disk fails. Writing the data to multiple locations on the hard disks can also slow overall system performance.
- RAID 1 - Error correction. It may be considered by some people as a separate configuration, however other people suggest that error correction, also called fault tolerance, is actually a benefit of Mirroring. In either case, because the same data is stored in two or more places on multiple drives, it can be checked for problems and fixed.
- RAID 0 - Striping. In striping, data is split apart and stored on more than one physical disk. This striped array improves read / write performance and gives you additional storage space, but offers no file redundancy. Because there is no error checking, if one disk fails, all information on that drive is lost and is unrecoverable.
Does HP recommend using a RAID array?
Some HP notebook PCs have multiple hard disk, however they are configured as a single drive. For the majority of the home and small business notebook computers, HP does not encourage or support the use of a RAID array.
For a business that has a specific need for RAID, there is a BIOS setting, enable RAID , that allows the computer to be reconfigured. Unless you have the specific technical knowledge, attempting to set up a RAID array may cause problems and is not recommended.
For additional information on RAID, you can search the internet for the topics: Server Architecture or Distributed Computing Systems , or visit the IEEE Organization (English only) web sites.