When you read “RAID”, it seems to have a very strong connotation to it. Sounds primal and full of action. The term originally was defined as Redundant Array of Inexpensive Disks. Okay, so maybe that wasn’t exactly what you were expecting out of RAID. Over the years it’s changed and now refers to a Redundant Array of Independent Disks. It uses multiple disks in order to provide fault tolerance, improve overall performance, and increase storage capacity in a system. RAID works by placing data on multiple disks and allowing input/output (I/O) operations to overlap in a balanced way, thus improving performance.
There are different RAID levels, each optimized for a specific situation:
Level 0: Striped disk array without fault tolerance. This provides data striping by spreading out blocks of each file across multiple disk drives, without redundancy. This will improve performance, but it does not deliver fault tolerance. If one drive fails, then all data will be lost.
Level 1: Mirroring and duplexing provides the read transaction rate of single disks, except twice as much. It also has the same write transaction rate as single disks.
Level 2: Error-correcting coding is rarely used. It stripes data at the bit level rather than the block level.
Level 3: Bit-interleaved parity is also rarely used. This third level provides byte-level striping with a dedicated parity disk. It cannot service simultaneous multiple requests.
Level 4: Dedicated parity drive is a commonly used implementation of RAID. In this level, striping is provided with a parity disk. If a data disk fails, the parity data is used to create a replacement disk. One disadvantage is that the parity disk can create write bottlenecks.
Level 5: Block interleaved distributed parity is by far the most common RAID configuration. It results in excellent performance and good fault tolerance, all by supplying data striping at the byte level, as well as stripe error correction information. It results in excellent performance and good fault tolerance.
Level 6: Independent data disks with double parity is frequently used with parity data distributed across all disks.
Level 10: A stripe of mirrors, which is not one of the original RAID levels. In this level, multiple RAID 1 mirrors are created and a RAID 0 stripe is created over these.
I know what you are thinking. “What happened to levels 7, 8, 9?” Think of them as the 5th member of the Beatles? Unnecessary.
When it comes to deciding which RAID level is the right one for you, it depends on whether you are using it for performance or fault tolerance. Or maybe it’s a little of both.
