+RAID

An acronym for Redundant Array of Independent Disks. RAID is two or more drives that function together to increase performance and capacity. RAID provides error recovery and fault tolerance for data. Types of RAID include Serial ATA & IDE . Although NAS network storage devices can perform RAID functions, they are not technically RAID units since most contain a separate processor and/or an O/S.

+RAID 0

RAID Level 0: "Disk Striping"

RAID 0: Also known as "Disk Striping", is technically not a RAID level since it provides no fault tolerance. (Parity) Data is written in blocks across multiple drives, so one drive can be writing or reading a block while the next is seeking the next block. The advantages of RAID 0 is it’s high level of I/O performance because the I/Os are spread across multiple channels and drives. Because RAID 0 offers no fault tolerance, if one drive should fail, this will result a loss of all your data. This should never be used in a environment where data is mission critical.

*RAID 0 requires a minimum of two drives to initiate.

+RAID 1

RAID Level 1: "Disk Mirroring"

RAID 1: Known as "Disk Mirroring" provides redundancy by fully duplicating drive data to all other drives in the array. If one drive fails, the others contain exact duplicate of the data and the RAID can switch to using the mirror drive with no lapse in user accessibility. The disadvantages of mirroring are no improvement in data access speed, and capacity is low. However, it provides the best protection of data since the array management software will simply direct all application requests to the surviving disk members when a member of disk fails.

RAID level 1 provides both very high data reliability and continued data availability in the event of a failure of any array member. When a RAID level 1 member disk fails, array management software simply directs all application requests to the surviving member.

RAID level 1 is most suitable for data which reliability requirements are extremely high, or for data to which high performance access is required. RAID 1 offers 100% data redundancy and requires no rebuild time.