What is RAID?Hard Drive

RAID stands for Redundant Array of Independent Disks. RAID is a technology that allows a computer to use multiple hard drives working together as one. RAID can be configured to provide redundancy to prevent the loss of data if a hard drive fails, or can be configured to provide improved read/write speed, or a combination of both.

Although there are many configurations of RAID, there are only three that are of interest to home and small business users:

RAID1 (Mirroring)

RAID1 simply "mirrors" two or more hard drives - they're kept perfectly identical at all times. Anything written to the drives is written to the same place on both drives at the same time. This provides two major benefits:
1) If either drive ever fails, your data is still safe on the other drive.
2) When the system is reading information from the hard drives, it can read it from two drives at once, effectively cutting "read time" in half. However, write speed is still the same as with a single drive (as the system has to write all of the data for a given operation to both drives).

RAID0 (Performance)

RAID0 is known as "striping". With a two-drive RAID0 array, each file on the system is split in half, with one half residing on each hard drive. This means the system can both read and write data twice as fast as normal, by writing half of each file to each drive, and reading from two drives at once. However, the down-side is that if either drive fails, all of the data is lost - therefore, a RAID0 system mandates frequent backups. Computer Works Northwest can setup a RAID0 with a third hard drive for automated backup.

RAID5 (Striping with Parity)

RAID5 is similar to a combination of RAID1 and RAID0. Raid5 requires at least three hard drives. The first two are configured just like a RAID0, while the third drive holds "parity data" that can be used to recover the data on either of the two main drives if they were to fail.
This provides most of the speed benefits of RAID0, while retaining the redundancy of RAID1: if any of the three drives is to fail, the data is still safe. A fourth drive can be added (known as a "hot spare") to allow the system to re-construct the lost data from the failed hard drive automatically, providing an extremely high level of reliability.
RAID5 is recommended for server applications and scenarios that require high-reliability, high-volume data storage.