A parity drive stores parity data for redundancy and backup in a RAID system. It provides extra storage of “parity bits” used to back up major drives. The parity unit works by storing parity bits, which can be used to recreate missing data if a storage drive fails.
A parity drive is a storage device used as part of a computer system that contains parity data for redundancy and backup purposes. This is commonly part of a redundant independent disk array (RAID), where one or more disk drives are linked together to act as a single system. When data is stored on these devices, parity information can be created for later use if one of the disks fails. A parity drive is not necessarily part of every RAID configuration, but it allows for simple and effective data recovery.
The basic function of a parity drive is to provide extra storage of “parity bits,” which are chunks of data used to back up the major drives in a disk array. An array is a computer configuration in which multiple disks, such as two or more hard drives, are connected together and used as a single storage system. While different methods are used for this, a RAID is among the most common forms. There are various types of RAID, and more complex “levels” often include the use of a parity drive to provide effective backup and information redundancy.
A parity unit works through the use of parity bits which are stored on it. The simplest example of how parity bits work is in a RAID or other system that uses three drives total. Two of the drives would be used as actual data storage disks, while the third would function as a parity drive. Whenever data is saved to the RAID, each piece of information is split in half, with one part going to one drive and the other part to the second.
Computer data consists of bits, which are binary data represented by ones or zeros. Whenever information is stored on a system with a parity unit, one bit of each unit of storage is added to the other. If the result is an even number, a parity bit with value zero is stored in the parity device, while an odd result creates the value one. This can then be used if one of the storage drives fails, to recreate the missing data in order to restore what has been lost.
For example, a ‘1’ on one device and a ‘0’ on the other would result in a ‘1’ being stored on the parity unit, as this is an odd value when added together. If the storage drive with data “0” becomes damaged, it can be replaced with a new blank disk. The system can then examine the existing data, find the remaining “1” in the data storage, compare it to the “1” in the parity device, and recognize that a “0” needs to be recreated to recover the lost data. This is redundancy and allows an array to effectively recover data even if part of the original system is lost.
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