What is RAID? List three features of RAID level 3.
RAID (Redundant Array of Independent Disks) is a technology that allows multiple hard disk drives to be combined into a single logical unit to improve performance, reliability, and capacity. The concept of RAID was introduced in the 1980s as a way to overcome the limitations of individual hard drives in terms of performance, reliability, and capacity.
RAID technology achieves its performance and reliability benefits by distributing data across multiple disks, using various techniques such as data striping, mirroring, or parity. Each RAID level has its own unique combination of these techniques, which offers different trade-offs between performance, data protection, and capacity utilization.
One of the most popular RAID levels is RAID level 3, which uses byte-level striping with a dedicated parity disk. Here are three features of RAID level 3:
Data Striping: RAID level 3 uses byte-level striping, which means that data is spread across multiple disks at the byte level. This improves performance by allowing multiple disks to work together to read or write data simultaneously. The data is broken down into blocks or stripes of a fixed size, and each stripe is written to a different disk. This means that the data can be read or written in parallel across all disks, which results in improved performance compared to a single disk.
Dedicated Parity Disk: RAID level 3 uses a dedicated parity disk to store parity information. Parity is a mathematical algorithm that is used to calculate the contents of missing or damaged data. The parity disk contains the XOR value of the corresponding data bytes on the other disks in the array. For example, if disk 1 and disk 2 contain the same data block, then the parity disk will contain the XOR value of those two blocks. In the event of a disk failure, the missing data can be reconstructed using the parity information on the dedicated parity disk.
High Performance for Sequential Reads: RAID level 3 is optimized for high performance when reading large sequential files, such as video or audio files. This is because sequential reads involve reading large blocks of data in a linear fashion, which can be spread across multiple disks and read in parallel. However, RAID level 3 may not be as efficient for random access operations, such as database queries or file searches, since these operations involve accessing data at different locations on the disks, which may not be located in the same stripe.
In conclusion, RAID is a technology that allows multiple hard disk drives to be combined into a single logical unit to improve performance, reliability, and capacity. RAID level 3 is a popular RAID configuration that uses byte-level striping with a dedicated parity disk. The key features of RAID level 3 include data striping, dedicated parity disk, and high performance for sequential reads.