RAID LEVELS

To secure your data from damage or crash this is how to setting up storage to meet your need. So, do not loose your data or you should be back here or some sites to find the article about how to recover your data ;))

A quick summary of the most commonly used RAID levels:

• RAID 0: Striped Set (2 disk minimum) without parity: provides improved performance and additional storage but no fault tolerance from disk errors or disk failure.
  
• RAID 1: Mirrored Set (2 disks minimum) without parity: provides fault tolerance from disk errors and single disk failure. Increased read performance occurs when using a multi-threaded operating system that supports split seeks, very small performance reduction when writing. Array continues to operate with one failed drive.
• RAID 3 and RAID 4: Striped Set (3 disk minimum) with Dedicated Parity: Provides improved performance and fault tolerance similar to RAID 5, but with a dedicated parity disk rather than rotated parity stripes. The single disk is a bottle-neck for writing since every write requires updating the parity data. One minor benefit is the dedicated parity disk allows the parity drive to fail and operation will continue without parity or performance penalty.
• RAID 5: Striped Set (3 disk minimum) with Distributed Parity: Distributed parity requires all but one drive to be present to operate; drive failure requires replacement, but the array is not destroyed by a single drive failure. Upon drive failure, any subsequent reads can be calculated from the distributed parity such that the drive failure is masked from the end user. The array will have data loss in the event of a second drive failure and is vulnerable until the data that was on the failed drive is rebuilt onto a replacement drive.
• RAID 6: Striped Set (4 disk minimum) with Dual Distributed Parity: Provides fault tolerance from two drive failures; array continues to operate with up to two failed drives. This makes larger RAID groups more practical. This is becoming a popular choice for SATA drives as they approach 1 Terabyte in size. This is because the single parity RAID levels are vulnerable to data loss until the failed drive is rebuilt. The larger the drive, the longer the rebuild will take. With dual parity, it gives the array time to rebuild onto a large drive with the ability to sustain another drive failure