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arrow 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.

arrow RAID Comparison Chart

　RAID Level
Min Drives
Protection
Description
Strengths
Weaknesses
Typical Apps
　RAID 0
2
None
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
2
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
3
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
4
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
4
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
6
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
8
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
High Availability Solutions, Mission Critical Apps, Servers with Large Capacity Requirements

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