RAID Level 0 requires a minimum of 2 drives to implement

Advantages

Disadvantages

RAID 0 implements a striped disk array, the data is broken down into blocks and each block is written to a separate disk drive

No parity calculation overhead is involved

Very simple design

Easy to implement

Not a 'True' RAID because it is NOT fault-tolerant

The failure of just one drive will result in all data in an array being lost

Should never be used in mission critical environments

RAID Level 1 requires a minimum of 2 drives to implement

Advantages

Disadvantages

One Write or two Reads possible per mirrored pair

100% redundancy of data means no rebuild is necessary in case of a disk failure, just a copy to the replacement disk

Simplest RAID storage subsystem design

Highest disk overhead of all RAID types (100%) - inefficient

Typically the RAID function is done by system software, loading the CPU/Server and possibly degrading throughput at high activity levels. Hardware implementation is strongly recommended.

Each bit of data word is written to a data disk drive (4 in this example: 0 to 3). Each data word has its Hamming Code ECC word recorded on the ECC disks. On Read, the ECC code verifies correct data or corrects single disk errors.

Advantages

Disadvantages

'On the fly' data error correction

Extremely high data transfer rates possible

The higher the data transfer rate required, the better the ratio of data disks to ECC disks

Very high ratio of ECC disks to data disks with smaller word sizes - inefficient

Entry level cost very high - requires very high transfer rate requirement to justify.

No commercial implementations exist.

The data block is subdivided ('striped') and written on the data disks. Stripe parity is generated on Writes, recorded on the parity disk and checked on Reads.
RAID Level 3 requires a minimum of 3 drives to implement

Advantages

Disadvantages

Very high Read data transfer rate

Very high Write data transfer rate

Disk failure has an insignificant impact on throughput

Low ratio of ECC (Parity) disks to data disks means high efficiency

Transaction rate equal to that of a single disk drive at best (if spindles are synchronized)

Controller design is fairly complex

Very difficult and resource intensive to do as a 'software' RAID

Each entire block is written onto a data disk. Parity for same rank blocks is generated on Writes, recorded on the parity disk and checked on Reads.
RAID Level 4 requires a minimum of 3 drives to implement

Advantages

Disadvantages

Very high Read data transaction rate

Low ratio of ECC (Parity) disks to data disks means high efficiency

High aggregate Read transfer rate

Low ratio of ECC (Parity) disks to data disks means high efficiency

Quite complex controller design

Worst Write transaction rate and Write aggregate transfer rate

Difficult and inefficient data rebuild in the event of disk failure

Block Read transfer rate equal to that of a single disk

Each entire data block is written on a data disk; parity for blocks in the same rank is generated on Writes, recorded in a distributed location and checked on Reads.RAID Level 5 requires a minimum of 3 drives to implement

Advantages

Disadvantages

Highest Read data transaction rate

Medium Write data transaction rate

Low ratio of ECC (Parity) disks to data disks means high efficiency

Good aggregate transfer rate

Disk failure has a medium impact on throughput

Most complex controller design

Difficult to rebuild in the event of a disk failure (as compared to RAID level 1)

Individual block data transfer rate same as single disk

Each entire data block is written on a data disk; parity for blocks in the same rank is generated on Writes, recorded in a distributed location and checked on Reads.RAID Level 5 requires a minimum of 3 drives to implement

Advantages

Disadvantages

RAID 6 is essentially an extension of RAID level 5 which allows for additional fault tolerance by using a second independent distributed parity scheme (two-dimensional parity)

Data is striped on a block level across a set of drives, just like in RAID 5, and a second set of parity is calculated and written across all the drives; RAID 6 provides for an extremely high data fault tolerance and can sustain multiple simultaneous drive failures

Perfect solution for mission critical applications

Very complex controller design

Controller overhead to compute parity addresses is extremely high

Very poor write performance

Requires N+2 drives to implement because of two-dimensional parity scheme

Fully implemented process oriented real time operating system resident on embedded array control microprocessor.
RAID 7 is a registered trademark of Storage Computer Corporation.

Advantages

Disadvantages

Overall write performance is 25% to 90% better than single spindle performance and 1.5 to 6 times better than other array levels

Host interfaces are scalable for connectivity or increased host transfer bandwidth

Small reads in multi user environment have very high cache hit rate resulting in near zero access times

No extra data transfers required for parity manipulation

One vendor proprietary solution

Extremely high cost per MB

Very short warranty

Not user serviceable

Power supply must be UPS to prevent loss of cache data

RAID Level 10 requires a minimum of 4 drives to implement

Advantages

Disadvantages

RAID 10 is implemented as a striped array whose segments are RAID 1 arrays

RAID 10 has the same fault tolerance as RAID level 1

RAID 10 has the same overhead for fault-tolerance as mirroring alone

Excellent solution for sites that would have otherwise gone with RAID 1 but need some additional performance boost

Very expensive / High overhead

All drives must move in parallel to proper track lowering sustained performance

Very limited scalability at a very high inherent cost

RAID Level 53 requires a minimum of 5 drives to implement

Advantages

Disadvantages

RAID 53 should really be called 'RAID 03' because it is implemented as a striped (RAID level 0) array whose segments are RAID 3 arrays

RAID 53 has the same fault tolerance as RAID 3 as well as the same fault tolerance overhead

High data transfer rates are achieved thanks to its RAID 3 array segments

Maybe a good solution for sites who would have otherwise gone with RAID 3 but need some additional performance boost

Very expensive to implement

All disk spindles must be synchronized, which limits the choice of drives

Byte striping results in poor utilization of formatted capacity

RAID Level 0+1 requires a minimum of 4 drives to implement

Advantages

Disadvantages

RAID 0+1 is implemented as a mirrored array whose segments are RAID 0 arrays

RAID 0+1 has the same fault tolerance as RAID level 5

RAID 0+1 has the same overhead for fault-tolerance as mirroring alone

Excellent solution for sites that need high performance but are not concerned with achieving maximum reliability

RAID 0+1 is NOT to be confused with RAID 10. A single drive failure will cause the whole array to become, in essence, a RAID Level 0 array

Very expensive / High overhead

Very limited scalability at a very high inherent cost

All drives must move in parallel to proper track lowering sustained performance