RAID 0, RAID 1, RAID 5, RAID 1+0 explained

RAID stands for Redundant Array of Independent Disks, originally known for Redundant Array of Inexpensive Disks.

Most commonly used RAID levels:

RAID 0

RAID 1

RAID 5

RAID 10 (also known as RAID 1+0)

In all the explanation below:

• A, B, C, D, E, F - represents blocks.
• p1, p2, p3 - represents parity.
• Parity - an error protection scheme which is a widely used method in information technology to provide fault tolerance in a given set of data.
• Strip - chunks of data are spread across multiple arrays, possibly all the drives in the system.

RAID LEVEL 0

RAID 0 – Blocks striped. No Mirror. No Parity.

Key points:

• Minimum 2 disks.
• Excellent performance ( as blocks are striped ).
• No redundancy ( no mirror, no parity ).
• not recommended to be used with critical systems.

RAID Level 1

RAID 1 – Blocks Mirrored. No Stripe. No Parity.

Key points:

• Minimum 2 disks.
• Good performance (no striping. no parity).
• Excellent redundancy (as blocks are mirrored).

RAID Level 5

RAID 5 – Blocks Striped. Distributed Parity.

Key points:

• Minimum 3 disks.
• Good performance ( as blocks are striped ).
• Good redundancy ( distributed parity ).
• Best cost effective option providing both performance and redundancy. Use this for DB that is heavily read oriented. Write operations will be slow.

RAID Level 10

RAID 10 – Blocks Mirrored. Blocks Striped.

Key points:

• Minimum 4 disks
• Also called "stripe of mirrors"
• Excellent redundancy ( as blocks are mirrored )
• Excellent performance ( as blocks are striped )
• If you can afford the dollar, this is the BEST option for any mission critical applications (especially databases).

Detailed explanation on RAID levels @ http://en.wikipedia.org/wiki/Standard_RAID_levels