The term parity is used for the system memory error detection. The concept of RAID parity is similar to the concept to parity RAM. The principle of RAID parity is simple. For example, the RAID parity can be explained as consider the N pieces of data and compute extra piece of data for each of the following. Then take N+ 1 piece of data and try to store it in N+1 drives. You may have a chance to lose any of the N+ 1 of data, you can use remaining of the data regardless in which piece may be lost. The term parity protection is used with striping in order to avoid, the loss of N pieces of data and can be used for bytes distributed across the drives in the array.

The parity information can be easily store on a separate or a dedicated drive or data across all the drives. The term parity calculation is used when a logical operation such as XOR or OR logical operator is true. XOR operator is true if one of its operands is true. The truth table of the operators is used for mirroring redundancy technique, generally for RAID level 1, to provide data protection. The advantages of mirroring are well-suited for certain RAID implementations. The implementation of the RAID Parity has a high cost, because the drives has a duplicate data and improve performance for many applications.

A different way of protecting data is provided as an alternate to mirroring. The redundancy of information is calculated from the actual data values. The XOR is a logical operation that if is used twice in a row. Suppose, If you want to calculate the problem such as A XOR B we can say that the A XOR B XOR B = A and this property is used for parity calculation under RAID. Suppose, we have four data elements, D1, D2, D3 and D4, we can easily calculate the parity data of D1 XOR D2 XOR D3 XOR D4 and if we know any four of D1, D2, D3, D4, the deployment parity can be XOR. The mirroring, parity has some advantages and disadvantages. The advantage of the RAID is to protect data from array failing without requiring waste of drives that contains redundancy information. Striping with parity also allows you to take advantage of the performance advantages of striping. Striping has a disadvantage with RAID parity such as complexity.

The hardware controller which performs calculations is required for high performance of the software RAID with striping and parity of the system will be dragged down while you can recover from a lost drive under parity, the missing data all has to be rebuilt, which has its own complications; data recovery from a lost mirrored drive is comparatively simple.

The RAID levels such as RAID 3, RAID5 and RAID 7 uses a concept which is exactly similar to parity but which is not exactly the same as the RAID parity. The main aim is to use the RAID parity is to better the performance in a RAID. RAID improves performance in different ways and buy RAID parity the performance is tremendously increased to very large extend. As a result the RAID parity is used for higher levels of RAID in which accuracy of the application performance matters to a very large extend.

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