What is RAID and Clacification of RAID0,RAID1, RAID5 ,RAID6, RAID10, RAID50, RAID60.

What is RAID ?RAID is stand for Redundant Array of Independent Disks. RAID is now used as an umbrella term for computer data storage schemes that can divide and replicate data among multiple hard disk drives. RAID's various designs all involve two key design goals: increased data reliability or increased input/output performance. When multiple physical disks are set up to use RAID technology, they are said to be in a RAID array. This array distributes data across multiple disks, but the array is seen by the computer user and operating system as one single disk. RAID can be set up to serve several different purposes.

Using Multiple Hard Drives for Performance and Reliability

or others for RAID

RAID is a solution that was developed originally for the network server market as a means of creating large storage at a lower cost. Essentially, it would take multiple lower cost hard drives and put them together through a controller to provide a single larger capacity drive. This is what RAID stands for: redundant array of inexpensive drives or disks. To achieve this, specialized software and controllers were needed to manage the data being split between the various drives. Eventually the processing power of your standard computer system allowed the features to filter their way into the personal computer market.

Now a RAID storage can be used for three distinct purposes. These include capacity, security and performance. Capacity is a simple one that is typically involved in most every type of RAID setup used. For instance, two hard drives can be linked together as a single drive to the operating system effectively making a virtual drive that is twice the capacity. Performance is another key reason for using a RAID setup on a personal computer. In the same example of two drives being used as a single drive, the controller can split a data chunk into two parts and then put each of those parts on a separate drive. This effectively doubles the performance of writing or reading the data on the storage system. Finally, RAID can be used for data security. This is done by by using some of the space on the drives to essentially clone the data that is written to both drives. Once again, with two drives we can make it so that the data is written to both drives. Thus, if one drive fails, the other still has the data.

Typical Apps  RAID 0
Data striping without redundancy . Highest performance No data protection; One drive fails, all data is lost
High End Workstations, Data Logging, Real-Time Rendering, Transitory Data

 RAID 1
Single Drive Failure
Disk mirroring, Very high performance; Very high data protection; Very good on write performance
High redundancy cost overhead; Because all data is duplicated, twice the storage capacity is required
Operating Systems, Transactional Databases

 RAID 5
Single Drive Failure , Block-level data striping with distributed parity
Best cost/performance for transaction-oriented networks, Very high performance, very high data protection; Supports multiple simultaneous reads and writes, Can also be optimized for large, sequential requests
Write performance is slower than RAID 0 or RAID 1
Data Warehousing, Web, Archiving, Basic File Servers, Disk Backup

 RAID 6
2 Drive Failure
Same as RAID 5 with x2 Parity distributed across an extra drive
Offers Solid Performance with the additional fault tolerance of allowing availability to data if 2 disks in a RAID group to fail. Recommended to use more drives in RAID group to make up for performance and disk utilization hits compared to RAID 5
Must use a minimum of 5 drives with 2 of them used for parity so disk utilization is not as high as RAID 3/5. Performance is slightly lower than RAID 5
High Availability Solutions, Mission Critical Apps, Servers with Large Capacity Requirements

 RAID 10
1 Disk Per Mirrored Stripe (not same mirror)
Combination of RAID 0 (data striping) and RAID 1 (mirroring)
Highest performance, highest data protection (can tolerate multiple drive failures)
High redundancy cost overhead; Because all data is duplicated, twice the storage capacity is required; Requires minimum of four drives
Databases, Application Servers

RAID 50
1 Disk Per Mirrored Stripe
Combination of RAID 0 (data striping) and RAID 5 (Single Parity Drive)
Highest performance, highest data protection (can tolerate multiple drive failures)
High redundancy cost overhead; Because all data is duplicated, twice the storage capacity is required; Requires minimum of four drives
Databases, File Servers, Application Servers,

 RAID 60
2 Disks Per Mirrored Stripe
Combination of RAID 0 (data striping) and RAID 6 (Dual Parity Drives)
Highest performance, highest data protection (can tolerate multiple drive failures)
High redundancy cost overhead; Because all data is duplicated, twice the storage capacity is required; Requires minimum of four drives












Root Extension of  RAID Disk Drive:
High Availability Solutions, Mission Critical Apps, Servers with Large Capacity Requirements

I've discussed the various pros and cons of each of the levels of RAID that can be used on personal computers but there is another issue that many people don't realize when it comes to creating RAID drive setups. Before a RAID setup can be used, it first must be constructed either by the hardware controller software or within the software of the operating system. This essentially initializes the special formatting required to properly track how the data will be written and read on the drive.

This probably doesn't sound like a problem but it is if you even need to change how you want your RAID array configured. For instance, say you are running low on data and want to add an extra drive for either a RAID 0 or RAID 5 array. In most cases, you won't be able to without first reconfiguring the RAID array which will also remove any of the data that was stored in those drives. This means that you have to fully back up your data, add the new drive, reconfigure the drive array format that drive array and then restore your original data back to the drive. That can be an extremely painful process. As a result, make sure you really have the array setup up the way you want to the first time you do it.