What is Raid?

BWI July 2008 Newsletter

What is RAID?

RAID: Redundant Array of Independent (Inexpensive) Disks

Until you have experienced the loss of data, you may not realize that hard drives don't last forever. Hard drives contain several moving parts that eventually wear out over time from general use. A time will come when your hard drive will fail. To prevent catastrophic data loss, you need a sound backup plan that should include regular backups of your system hard drives. RAID should be the first level of protection in a backup strategy.

RAID lets you store data on multiple drives. Each time data is written to the RAID it is written to each of the drives in the array rather than just to a single drive. The data is divided into segments that allow data redundancy in a fault tolerant environment. RAID units can generally be set to one of two different operating modes, RAID0 (Striping) and RAID1 (Mirroring). RAID0 is used to increase data transfer rates and resulting system performance. RAID1 provides data redundancy when writing to the RAID.

RAID 0: Striping

This RAID mode is designed for speed. It does not have any fault tolerance or data protection. At least two drives are required for this mode. If one drive in RAID 0 were to fail, then there would be no way to recover data.

RAID 1: Mirroring

This RAID mode is designed for data integrity and fault tolerance. This mode is not as fast as RAID 0. However, RAID 1 uses the second drive (target drive) as a copy of the first drive (source drive).

RAID Basic Operation Method Hard Disk Available Capacity Data Reliability Data Transfer Speed Minimum Number of Hard Disks
0 Striping data across each drive. Total capacity of all HDDs Low (Normal for one HDD) Faster 2
1 Mirroring, a copy of the source drive. Half capacity of all HDDs. High (Redundant) Slower 2

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