RAIDpariteetti

RAIDpariteetti, often referred to as RAID parity, is a technique used in RAID (Redundant Array of Independent Disks) storage systems to provide fault tolerance. It involves calculating and storing redundant data across multiple drives in an array. This redundant data, known as parity information, allows the system to reconstruct lost data if one or more drives fail.

The core concept behind parity is a mathematical calculation, typically XOR (exclusive OR), applied to the data blocks on the drives. For example, in a RAID 5 array, data blocks are striped across multiple disks, and a parity block is generated for each stripe. This parity block contains information derived from the data blocks in that stripe. If a drive containing a data block fails, the system can use the remaining data blocks and the parity block to recalculate the missing data.

Different RAID levels employ parity in various ways. RAID 4, for example, uses a dedicated parity disk. RAID 5 distributes parity blocks across all data disks. RAID 6 enhances fault tolerance further by calculating and storing two independent parity blocks for each stripe, allowing for the failure of up to two drives. The primary benefit of using parity is its ability to recover data without requiring a full data mirror, thus offering a more cost-effective solution for data protection compared to mirroring alone. However, calculating and accessing parity information can introduce a performance overhead, especially during write operations.