RAID
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RAID stands for, "Redundant Array of Inexpensive Disks" and it combines two or more physical hard disks into a single logical unit by using either special hardware or software. Hardware solutions often are designed to present themselves to the attached system as a single hard drive, and the operating system is unaware of the technical workings. Software solutions are typically implemented in the operating system, and again would present the RAID drive as a single drive to applications.
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RAID 0
RAID 0 is the lowest level of RAID and is named 0 because it doesn't actually provide any level of redundancy for the data stored in the array. RAID 0 employs a method called 'striping'. Striping takes a single chunk of data, like a graphic image, and spreads that single chunk of data across multiple drives. The advantage of striping lies in an improved performance. Two times the amount of data can be written in a given time frame to the two drives compared to that same data being written to a single drive.
RAID 1
RAID 1 was the first real version of RAID. It is capable of performing a simple yet full form of redundancy for data through a process called 'mirroring'. This form generally requires two individual drives of similar capacity. One drive is the active drive while the secondary drive is the mirror. When data is written to the active drive, the same data is written to the mirror drive.
RAID 5
RAID 5 is the most powerful version of RAID that can be found in a desktop computer system. Generally it requires the form of a hardware controller card to manage the array, however some desktop operating systems can create these using software. This method uses a form of striping with parity in order to maintain data redundancy. A minimum of three drives is required to build a RAID 5 array and they should be identical drives to ensure the best performance.
RAID 10
In RAID 10, the first two drives in the set are mirrored together. The second two drives create another set of disks that are a mirror of one another but store striped data with the first pair. This setup is a type of nested RAID. Drives 1 and 2 are a RAID 1 mirror while drives 3 and 4 are also a mirror. These two sets are then setup as stripped array.
