Raid Levels

Front 1

RAID 0

Back 1

- Stripe set without parity
- two or more drives
- can use different types of drives
- writes identically sized strips of data to each disk
- fastest RAID configuration
- no data redundancy

Front 2

RAID 1
Disk Mirroring

Back 2

- exactly duplicates first disk to second disk
- continuously writes data identically to both disks
- both disks on one controller
- faster than RAID 4
- complete data redundancy

Front 3

RAID 1
Disk Duplexing

Back 3

- exactly duplicates first disk to second disk
- continuously writes data identically to both disks
- each disk on it's own controller
- faster than RAID 4
- complete data redundancy

Front 4

RAID 4

Back 4

- Independent data disks with shared parity
- rarely used
parity for same-rank blocks is written to the parity disk on writes and checked on reads
- very fast read rate
- slow write and transfer rates
- slow disk rebuilds

Front 5

RAID 5

Back 5

Stripe set with parity
- stripes data and parity in large blocks across all disks
- requires at least 3 disks of the same size
- faster and more redundant than RAID 4
- faster reads than RAID 1, unless a disk has failed
- slower writes than RAID 1
- fault tolerant unless 1 disk has already failed
- can rebuild itself once a failed disk has been replaced without using backup tapes