Features	RAID 0	RAID 1	RAID 1E	RAID 5	RAID 5EE
Minimum # Drives	2	2	3	3	4
Data Protection	No Protection	Single-drive failure	Single-drive failure	Single-drive failure	Single-drive failure
Read Performance	High	High	High	High	High
Write Performance	High	Medium	Medium	Low	Low
Read Performance (degraded)	N/A	Medium	High	Low	Low
Write Performance (degraded)	N/A	High	High	Low	Low
Capacity Utilization	100%	50%	50%	67% - 94%	50% - 88%
Typical Applications	High End Workstations, data logging, real-time rendering, very transitory data	Operating System, transaction databases	Operating system, transaction databases	Data warehousing, web serving, archiving	Data warehousing, web serving, archiving

Features	RAID 6	RAID 10	RAID 50	RAID 60
Minimum # Drives	4	4	6	8
Data Protection	Two-drive failure	Up to one disk failure in each sub-array	Up to one disk failure in each sub-array	Up to two disk failure in each sub-array
Read Performance	High	High	High	High
Write Performance	Low	Medium	Medium	Medium
Read Performance (degraded)	Low	High	Medium	Medium
Write Performance (degraded)	Low	High	Medium	Low
Capacity Utilization	50% - 88%	50%	67% - 94%	50% - 88%
Typical Applications	Data archive, backup to disk, high availability solutions, servers with large capacity requirements	Fast databases, application servers	Large databases, file servers, application servers	Data archive, backup to disk, high availability solutions, servers with large capacity requirements

Types of RAID

Types of RAID	Software-Based	Hardware-Based	External Hardware
Description	Best used for large block applications such as data warehousing or video streaming. Also where servers have the available CPU cycles to manage the I/O intensive operations certain RAID levels require. Included in the OS, such as Windows®, Netware, and Linux. All RAID functions are handled by the host CPU which can severely tax its ability to perform other computations.	Best used for small block applications such as transaction oriented databases and web servers. Processor-intensive RAID operations are off-loaded from the host CPU to enhance performance. Battery-back write back cache can dramatically increase performance without adding risk of data loss.	Connects to the server via a standard adapter. RAID functions are performed on a microprocessor located on the external RAID adapter independent of the host.
Advantages	Low price Only requires a standard adapter	Data protection and performance benefits of RAID More robust fault-tolerant features and increased performance versus software-based RAID	OS independent Build high-capacity storage systems for highend servers

RAID 0

RAID 0, also called striping, is a scheme where data is divided into blocks and distributed across the drives in the array. This level does not provide redundancy, so consequently it has the best overall performance. For this reason, it is not suitable for mission critical situations, but is best used in situations where improved performance is the primary driver.

RAID 1

There are two implementations of RAID 1: mirroring and duplexing. With both schemes, data is duplicated on a second disk. Mirroring uses a single drive controller, while duplexing uses two controllers. In the event of a single drive failure, data can be read or written from the other drive, providing fault tolerance. And in the case of duplexing, even a controller failure won't bring down the system. However, there won't be any performance improvements, but instead, a potential decrease in write performance.

RAID 5

RAID 5 is called striping with distributed parity. Data and parity or error detection and correction code,  is striped across three or more drives. Parity is stored on a dedicated drive, which results in less available storage space. If a drive fails, data can be recovered from the remaining data blocks and the parity information. This level also features improved read and write performance because data can be read or written simultaneously across multiple drives.

RAID 0+1 (01)

This is the first of the hybrids, which simply combines other RAID levels. RAID 0+1 (also called 01) mirrors and stripes data simultaneously. Combining striping and mirror marries high performance with fault tolerance, making this one of the most popular levels. Under this scheme, two striped arrays are created, and one acts as the mirror to the other. This requires a minimum of four drives.

RAID 1+0 (10)

With this RAID level, data is mirrored and striped simultaneously. Most often, this is implemented with four drives, and one mirrored drive set is striped. This provides even higher fault tolerance and performance. RAID 10 differs from 01 in that things are reversed. Where 01 is a mirror of stripes, 10 is a stripe of mirrors.