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Wednesday, 11 March 2015

RAID Types Explained

RAID 0, also known as disk striping, is a technique that breaks up a file and spreads the data across all the disk drives in a RAID group.
The benefit of RAID 0 is that it improves performance. Because striping spreads data across more physical drives, multiple disks can access the contents of a file, allowing writes and reads to be completed more quickly. A drawback to RAID 0 is that it does not have parity. If a drive should fail, there is no redundancy and all data would be lost. RAID 0 requires at least two physical disks.
RAID 1: RAID 1 is called disk mirroring. All the data is written to at least two separate physical disks. The disks are essentially mirror images of each other. If one of the disks fails, the other can be used to retrieve data. Disk mirroring is good for very fast read operations. It's slower when writing to the disks, since the data needs to be written twice. RAID 1 requires at least two physical disks.
RAID 5 is a RAID configuration that uses disk striping with parity. Because data and parity are striped across all of the disks, no single disk is a bottleneck. Striping also allows users to reconstruct data in case of a disk failure. Reads and writes are more evenly balanced in this configuration, making RAID 5 the most commonly used RAID method. RAID 5 requires at least three physical disks.
RAID 6, also known as double-parity RAID, uses two parity stripes on each disk. It allows for two disk failures within the RAID set before any data is lost. RAID 6, also known as double-parity RAID, uses two parity stripes on each disk. It allows for two disk failures within the RAID set before any data is lost. This configuration offers very high fault- and drive-failure tolerance. It is used for environments that need long data retention periods, such as archiving. One disadvantage in using RAID 6 is that each set of parities must be calculated separately, which slows write performance. Implementing RAID 6 is also more expensive because of the two extra disks required for parity.
RAID 10, also known as RAID 1+0, combines disk mirroring and disk striping to protect data.
A RAID 10 configuration requires a minimum of four disks, and stripes data across mirrored pairs. As long as one disk in each mirrored pair is functional, data can be retrieved. If two disks in the same mirrored pair fail, all data will be lost because there is no parity in the striped sets. RAID 10 provides redundancy and performance, and is the best option for I/O-intensive applications. One disadvantage is that only 50% of the total raw capacity of the drives is usable due to mirroring.

Source:-
Techtarget