RAID stands for Redundant Array of Independent Disks or Redundant Array of Inexpensive Disks, depending on who you ask. It is a data storage technology that combines multiple physical disk drives into one or more logical units for data redundancy, performance improvement, or both.
RAID can be implemented using hardware or software, depending on your needs and budget. Hardware RAID uses a dedicated controller device to manage the disks and present them as logical units to the operating system. Software RAID uses the operating system’s drivers and utilities to perform the same functions.
RAID Levels
There are different RAID levels, each with its own advantages and disadvantages. The most commonly used levels are RAID 0, 1, 5, 6, and 10. Let’s take a look at each one briefly.
RAID 0: Striping
RAID 0 splits data across two or more disks without any redundancy. This means that if one disk fails, all data is lost. However, it also means that read and write operations are faster than with a single disk, as multiple disks can work in parallel. RAID 0 is suitable for applications that require high performance but can tolerate data loss.
RAID 1: Mirroring
RAID 1 duplicates data across two or more disks, creating an exact copy of each disk. This means that if one disk fails, another disk can take over without any data loss. However, it also means that write operations are slower than with a single disk, as each write must be performed on all disks. RAID 1 is suitable for applications that require high reliability but can sacrifice some performance.
RAID 5: Distributed Parity
RAID 5 distributes data and parity information across three or more disks. Parity information is used to reconstruct data in case of a disk failure. This means that RAID 5 can tolerate one disk failure without any data loss. However, it also means that write operations are slower than with RAID 0 or RAID 1, as parity information must be calculated and written on each disk. RAID 5 is suitable for applications that require a balance between reliability and performance.
RAID 6: Dual Parity
RAID 6 is similar to RAID 5 but uses two sets of parity information instead of one. This means that RAID 6 can tolerate two disk failures without any data loss. However, it also means that write operations are even slower than with RAID 5, as two sets of parity information must be calculated and written on each disk. RAID 6 is suitable for applications that require very high reliability but can sacrifice some performance.
RAID 10: Striping + Mirroring
RAID 10 combines RAID 0 and RAID 1 by creating stripes of mirrored disks. This means that RAID 10 offers both high performance and high reliability by splitting data across multiple disks while duplicating each stripe on another set of disks. However, it also means that half of the total disk capacity is wasted for redundancy purposes. Also, if two disks fail within the same stripe, all data is lost. RAID 10 is suitable for applications that require both high performance and high reliability.
Why Use RAID?
RAID offers several benefits over using single hard drives, such as:
– Improved cost – effectiveness because lower – priced disks are used in large numbers
– Increased computer speed after a crash, depending on the configuration
– Reads and writes can be performed faster than with a single drive with RAID configured using multiple disks.
– Allows for more redundancy in mirrored RAID configurations in that if one of the drives fails due to hardware failure, the other drive will still have the data.