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RAID Levels and Types
RAID, an acronym of Redundant Array of Independent (Inexpensive) Disks is the talk of the day. These are an array of disk to give more power, performance, fault tolerance and accessibility to the data, as a single storage system. It's not mere combination of disks but all the disks are combined providing standard MTBF (mean time before failure) reliability scheme; otherwise chances are performance would be affected drastically if disks are not combined as a single storage unit.
RAID Levels

All the RAID types and models are commonly classified as RAID levels, since RAID represented by a higher number is regarded to be superior, more efficient, high-performance array than the low numbered RAID.

Hence, high security feature of RAID also depends on the RAID level you are using. RAID arrays, not only, provide the users with maximum security and reliability but also make sure that if a disk fails no data is lost. The in-depth knowledge about RAID levels would help you through buying of RAID servers.

Let's briefly discuss here the main RAID levels and classes:
RAID 0 - Striping:
It is the Stripped Disk Array with no fault tolerance and it requires at least 2 drives to be implemented. Due to no redundancy feature, RAID 0 is considered to be the lowest ranked RAID level. Striped data mapping technique is implemented for high performance at low cost. The I/O performance is also improved as it is loaded across many channels. Regeneration, Rebuilding and functional redundancy are some salient features of RAID 0.
RAID 1 - Mirroring:
It is the Mirroring (Shadowing) Array meant to provide high performance. RAID 1 controller is able to perform 2 separate parallel reads or writes per mirrored pair. It also requires at least 2 drives to implement a non-redundant disk array. High level of availability, access and reliability can be achieved by entry-level RAID 1 array. With full redundancy feature available, need of readability is almost negligible. Controller configurations and storage subsystem design is the easiest and simplest amongst all RAID levels.
RAID 0+1:
It is the RAID array providing high data transference performance with at least 4 disks needed to implement the RAID 0+1 level. It's a unique combination of stripping and mirroring with all the best features of RAID 0 and RAID 1 included such as fast data access and fault tolerance at single drive level. The multiple stripe segments have added high I/O rates to the RAID performance and it is the best solution for maximum reliability.
It is the combination of Inherently Parallel Mapping and Protection RAID array. It's also known as ECC RAID because each data word bit is written to data disk which is verified for correct data or correct disk error when the RAID disk is read. Due to special disk features required, RAID 2 is not very popular among the corporate data storage masses, despite the extremely high data transference rates.
RAID 3 works on the Parallel Transfer with Parity technique. The least number of disks required to implement the RAID array is 3 disks. In the RAID 3, data blocks are striped and written on data drives and then the stripe parity is generated, saved and afterwards used to verify the disk reads. Read and write data transfer rate is very high in RAID 3 array and disk failure causes insignificant effects on the overall performance of the RAID.
RAID 4 requires a minimum of 3 drives to be implemented. It is composed of independent disks with shared parity to protect the data. Data transaction rate for Read is exceptionally high and highly aggregated. Similarly, the low ratio of parity disks to data disks indicates high efficiency.
RAIDS 5 is Independent Distributed parity block of data disks with a minimum requirement of at least 3 drives to be implemented and N-1 array capacity. It helps in reducing the write inherence found in RAID 4. RAID 5 array offers highest data transaction Read rate, medium data transaction Write rate and good cumulative transfer rate.
RAIDS 6 is Independent Data Disk array with Independent Distributed parity. It is known to be an extension of RAID level 5 with extra fault tolerance and distributed parity scheme added. RAID 6 is the best available RAID array for mission critical applications and data storage needs, though the controller design is very complex and overheads are extremely high.
RAID 7 is the Optimized Asynchrony array for high I/O and data transfer rates and is considered to be the most manageable RAID controller available. The overall write performance is also known to be 50% to 90% better and improved than the single spindle array levels with no extra data transference required for parity handling. RAID 7 is registered as a standard trademark of Storage Computer Corporation.
RAID 10:
RAID 10 is classified as the futuristic RAID controller with extremely high Reliability and performance embedded in a single RAID controller. The minimum requirement to form a RAID level 10 controller is 4 data disks. The implementation of RAID 10 is based on a striped array of RAID 1 array segments, with almost the same fault tolerance level as RAID 1. RAID 10 controllers and arrays are suitable for uncompromising availability and extremely high throughput required systems and environment.

With all the significant RAID levels discussed here briefly, another important point to add is that whichever level of RAID is used regular and consistent data backup maintenance using tape storage is must as the regular tape storage is best media to recover from lost data scene.




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