RAID Level Comparison Table

RAID Level RAID 0 RAID 1 RAID 3 RAID 5

Also Known As striping mirroring

striping with dedicated parity

striping with distributed parity

Fault Tolerance no yes yes yes

Redundancy Type none duplicate parity parity

Hot Spare Option no yes yes yes

Disks Required one or more two three or more three or more

Usable Capacity greatest least intermediate intermediate

Capacity Reduction none 50% capacity of one

disk capacity of one disk

Read Performance

fast (depends on number of disks) intermediate fast fast

Random Write Performance fastest intermediate slowest slow

Sequential Write Performance

fastest intermediate slow slowest

Typical Use

Rapid reads and writes with no need for fault tolerance. Provides high data throughput, especially for large files.

Mostly small random writes with fault tolerance. Appropriate for small databases or any other environment that requires fault tolerance but small capacity.

Mostly large, serial transfers with fault tolerance

Mostly small, random transfers with fault tolerance.

Provides high data throughput, especially for large files. Use RAID 5 for transaction processing applications because each drive can read and write independently. If a drive fails, PERC 3 uses the parity drive to recreate all missing information. Use also for office automation and online customer service that requires fault tolerance. Use for any application that has high read request rates but low write request rates.

Strong Points Provides increased data throughput for large files. No capacity loss penalty for parity.

Provides complete data redundancy. RAID 1 is ideal for any application that requires fault tolerance and minimal capacity.

Provides data redundancy, high read rates, and good performance in most environments. Provides redundancy with lowest loss of capacity.

Weak Points

Does not provide fault tolerance or high bandwidth. All data lost if any drive fails.

Requires twice as many disk drives. Performance is impaired during drive rebuilds.

Not well suited to tasks requiring lot of writes. Suffers more impact if no cache is used (clustering). Disk drive performance will be reduced if a drive is being rebuilt. Environments with few processes do not perform as well because the RAID overhead is not offset by the performance gains in handling simultaneous processes.

RAID Level RAID 1+0 RAID 3+0 RAID 5+0

Also Known As striping with mirrored arraysstriping with dedicated parity drives

striping with distributed parity

Fault Tolerance yes yes yes

Redundancy Type duplicate parity parity

Hot Spare Option yes yes yes

Disks Required for basic RAID 2 3 or more 3 or more

  Spans 2 arrays 4 6, 8, 10, 12, 14, or

16 6, 8, 10, 12, 14, or 16

  Spans 3 Arrays 6 9, 12, 15, 18, 21, or

24 9, 12, 15, 18, 21, or 24

  Spans 4 arrays 8 12, 16, 20, 24, 28,

or 32 12, 16, 20, 24, 28, or 32

  Spans 5 arrays 10 15, 20, 25, 30, 35,

or 40 15, 20, 25, 30, 35, or 40

Usable Capacity least intermediate intermediate

Capacity Reduction 50%

capacity of one disk for each array spanned

capacity of one disk for each array spanned

Read Performance intermediate fast fast

Random Write Performance intermediate slowest slow

Sequential Write Performance

intermediate slow slowest

Typical Use Mostly small random writes with fault tolerance and enhanced speed.Appropriate when used with data storage that needs 100% redundancy of mirrored arrays and that also needs the enhanced I/O performance of RAID 0 (striped arrays.) Works well for medium-sized databases or any environment that requires a higher degree of fault tolerance and moderate to medium capacity.

Mostly large, serial transfers with fault tolerance and enhanced speed

Mostly small, random transfers with fault tolerance and enhanced speed.Appropriate when used with data that requires high reliability, high request rates, and high data transfer and medium to large capacity.

Strong PointsProvides both high data transfer rates and complete data redundancy.

Provides high data throughput, data redundancy, and very good performance.

Weak Points Requires twice as many drives as all other RAID levels except RAID 1.

Requires 2 to 4 times as many parity drives as RAID 5.