Redundant Array of Independent Disks (RAID) is a technology that puts many hard drives together and improves on what one drive cannot do individually. Based on the user’s configuration mechanism, a RAID system can considerably increase computer speed, because the multiple hard drives will work together as a single drive. The user can as well use the RAID system to considerably increase reliability, enabling the computer work even after one of the hard drives crashes. Some RAID systems allow the user do both. This data visualization technology combines multiple hard drive components into single logical unit for performance or data redundancy purposes.
There are several ways through which data is distributed across the drives, known as RAID level based on the specific redundancy level and necessary performance. The different architectures or schemes are named RAID and followed by a number, for example RAID 1, RAID 2 etc. Each of the schemes provides a unique balance between the main targets namely: capacity, reliability, performance, and availability. All RAID levels exceeding RAID 0 help to protect against read errors with unrecoverable sectors, and in general failure of the while hard disk.
RAID 0 turns at least two of the drives involved into a single bigger, and quick performing storage unit. It helps to significantly increase chances that a crashed drive will lose all your data.
On saving a file, RAID 0 splits it into many sections and distributes it to the various drives. Because the drive heads are collaboratively working on many parts of the same file the array can easily read and write faster than if it were just one drive.
RAID 0 as well gives a user much storage. If using one terabyte of drives in this RAID array, you will have one 4 terabytes drive.
However, the four drives quadruple the chances of one of them crashing. Unfortunately, because each file is distributed to the four disks there are high chances of losing all data.
This arrangement the two drives involved reflect each other as in both contain similar data. If one of the drives fails the other will still be working. You cannot lose all files at once. For instance if you turn two drives into RAID 1 the resulting system will still have the speed and capacity of one system, meaning there will be extra protection for your data.
It is good not to consider RAID 1 a perfect data backup because a hard drive crash isn’t the only cause of data loss. Think of destruction by fire, burglary, getting attacked by Trojans, or making a single error but that hits the whole system.
This system comprises bit-level striping that has a highly dedicated Hamming-code capacity. The entire spindle disk rotation is fully synchronized and the data striped in such a way that every sequential bit is located on a separate drive. The Hamming-code parity gets calculated across each of the corresponding bits and is stored in one or more of the parity drives. This system was common in the past few years, and is no longer applicable in 2014 by any of the commercial systems.
RAID 3 is made up of byte-level striping that has dedicated parity. The entire disk spindle rotation gets synchronized and the data striped in a way that ensures each of the sequential byte is located on another different drive. The parity gets calculated across the corresponding bytes and is then stored on dedicated parity drives. RAID 3 still exists, but is not common.
RAID 4 comprises of block-level striping that has dedicated parity. This level was in the past few years common with NetApp, but has since been replaced with a unique implementation of RAID comprising of two parity disks named RAID-DP.
This is the most effective RAID system so far, combining the benefits of RAID 1 and RAID 0 such as extra security, capacity and speed. However, in this case you will need three drives and just two of the three will be used for storage.
Just like RAID 0, this system divides data into many sections and stores them in at least two drives, which leads to increased capacity and speed. RAID 5 devoted the third drive to parity, thus saving data about the other two drives’ information.
If by any chance one of the non-parity drives fails to work, the parity drive can easily look at the data in the working drive(S), and figure out what could have been stored on the dead one. As much as the RAID and computer will still work, the system’s working speed will reduce because of the extra calculations.
Unlike the above stated RAID system that depends on the error protection scheme known as parity to provide data tolerance for a specific data set. The RAID 6 system comprises of two separate parities based on multiplication and addition in a given Galois Field, or Reed-Solomon error correction.
And a final word to say here. If you want to set up your hard drives in a RAID array, make sure they are of a high-quality hard drive brand, as this will ensure the best performance and sustainable reliability.