Understanding the RAID System
RAID stands for "Redundant Array of Independent Disks or Redundant Array of Inexpensive Disks" (redundant collection of inexpensive / independent disks). RAID is a method of combining several small, inexpensive hard drives into a disk pool that provides better performance and resiliency than a single larger, more expensive drive. However, from a computer perspective, the disk grouping appears as a single disk.
Redundant data storage, which is the duplication of all or part of the data stored on drives, helps protect the fault tolerance of the drive pool. This way, if one drive fails, data is preserved on the other operational drives.
There are several forms of RAID devices, all offering some level of fault tolerance, each with a specific tradeoff in functionality and performance.
The two most common forms of RAID are RAID 1 and RAID 5, described below:
Also known as disk mirroring, RAID 1 provides default tolerance and full data redundancy, but it decreases overall capacity and does not improve performance.
RAID 1 requires a minimum of two hard drives. Several identical disks are created, which means that data is recorded on all of these disks, not just one.
If a drive fails, data is not lost because an identical drive replaces the failed drive. RAID 1 is ideal for dual drive configurations and for users who require full data redundancy.
Also known as parity aggregated volume, RAID 5 involves striped volume aggregation with distributed parity. It requires a minimum of three hard drives. The data is divided into tapes and stored on all disks. Parity data, which is used to regenerate lost data, is also striped across all drives.
The RAID 5 system is ideal for configurations with a minimum of three disks. It offers a combination of superior capacity and redundancy.
How do I choose the right RAID configuration?
For excellent fault tolerance, RAID 1 provides the best configuration.
RAID 1 fully mirrors or duplicates data on all hard drives, providing multiple copies of all data. However, the storage capacity is reduced to the size of a single disk.
For excellent fault tolerance and optimum performance, RAID 5 offers the best configuration.
RAID 5 provides fault tolerance, as well as high performance and high capacity. Transfer speeds are faster than RAID 3 or RAID 4. In the event of a drive failure, data is protected, but if the failure involves multiple drives, it is lost.