RAID (Redundant Array of Independent Disks) divides and replicates data across multiple disk drives. There are several types of RAID configurations: RAID 0 uses striping to improve performance but without redundancy; RAID 1 uses mirroring to provide redundancy with small performance costs; RAID 5 uses striping with parity bits for redundancy while using more disks than RAID 1. Higher numbered RAIDs like RAID 50 combine different RAID types. RAID improves performance and fault tolerance but is not a replacement for backups and cannot prevent data loss from viruses or other disasters.

2. RAID And Storage Arrays
Chris Pierce

3. Definitions:
Array - a systematic arrangement of objects.
RAID - Redundant Array of Independent Disks
In plain english please?
RAID is an umbrella term used for any method that
divides or replicates data across multiple hard disk
drives.

4. Types of RAID:
RAID 0 - Striped Disks
Disk 1 Disk 2 Data is thrown across both
disks allowing for increased
Data “A” RAID Controller
performance but with the
A1 A2 cost of 0 redundancy.
A3 A4
A5 A6

5. Types of RAID:
RAID 0 - Striped Disks
Disk 1 Disk 2 Data is thrown across both
disks allowing for increased
Data “A” RAID Controller
performance but with the
A1 A2 cost of 0 redundancy.
A3 A4
A5 A6

6. Types of RAID:
RAID 0 - Striped Disks
Disk 1 Disk 2 Data is thrown across both
disks allowing for increased
Data “A” RAID Controller
performance but with the
A2 cost of 0 redundancy.
A4
A6

7. Types of RAID:
RAID 1 - Mirroring Disks
Data is replicated across
Disk 1 Disk 2
both disks allowing for
Data “A” RAID Controller increased redundancy with
A1 A1 a only a small performance
cost.
A2 A2
A3 A3

8. Types of RAID:
RAID 1 - Mirroring Disks
Data is replicated across
Disk 1 Disk 2
both disks allowing for
Data “A” RAID Controller increased redundancy with
A1 A1 a only a small performance
cost.
A2 A2
A3 A3

9. Types of RAID:
RAID 1 - Mirroring Disks
Data is replicated across
Disk 1 Disk 2
both disks allowing for
Data “A” RAID Controller increased redundancy with
A1 A1 a only a small performance
cost.
A2 A2
A3 A3

10. Types of RAID:
RAID 1 - Mirroring Disks
Data is replicated across
Disk 1 Disk 2
both disks allowing for
Data “A” RAID Controller increased redundancy with
A1 A1 a only a small performance
cost.
A2 A2
A3 A3

11. Types of RAID:
RAID 5 - Striped Parity
Disk 1 Disk 2 Disk 3
Data “A” RAID Controller
A1 A2 P1
Data is striped across P2 A3 A4
multiple disks and a parity
bit is written for redundancy.
A5 P3 A6

12. Types of RAID:
RAID 5 - Striped Parity
Disk 1 Disk 2 Disk 3
Data “A” RAID Controller
A1 A2 P1
P2 A3 A4
A5 P3 A6

13. Types of RAID:
RAID 5 - Striped Parity
Disk 1 Disk 2 Disk 3
Data “A” RAID Controller
A1 A2 P1
P2 A3 A4
A5 P3 A6

14. Types of RAID:
RAID 5 - Striped Parity (Cont.)
Disk 1 Disk 2 Disk 3
010011 RAID Controller
Parity is checked across the
array. If the data written is
added to be even then the
parity bit is 0. If the data
written is odd, the parity bit
is set to 1

15. Types of RAID:
RAID 5 - Striped Parity (Cont.)
Disk 1 Disk 2 Disk 3
010011 RAID Controller
0 1
Parity is checked across the
array. If the data written is
added to be even then the 0 0
parity bit is 0. If the data
written is odd, the parity bit
is set to 1
1 1

16. Types of RAID:
RAID 5 - Striped Parity (Cont.)
Disk 1 Disk 2 Disk 3
010011 RAID Controller
0 1 1
Parity is checked across the
array. If the data written is
added to be even then the 0 0 0
parity bit is 0. If the data
written is odd, the parity bit
is set to 1
1 0 1

17. Types of RAID:
RAID 5 - Striped Parity (Cont.)
Disk 1 Disk 2 Disk 3
010011 RAID Controller
0 1 1
Parity is checked across the
array. If the data written is
added to be even then the 0 0 0
parity bit is 0. If the data
written is odd, the parity bit
is set to 1
1 0 1

18. Types of RAID:
RAID 5 - Striped Parity (Cont.)
Disk 1 Disk 2 Disk 3
010011 RAID Controller
0 1 1
Parity is checked across the
array. If the data written is
added to be even then the 0 0 0
parity bit is 0. If the data
written is odd, the parity bit
is set to 1
1 0 1

19. Other RAID Configurations:
Don’t be confused by RAID 50, RAID 10, RAID 51, or
other High Number RAID Configurations.
RAID 50 = RAID 5 + RAID 0
RAID 10 = RAID 1 + RAID 0
RAID 51 = RAID 5 + RAID 1

20. What RAID is NOT!
RAID is NOT data backup - Data can still
become damaged in a RAID array.
RAID is NOT immune to viruses and other
disasters that could potentially cause data loss.
RAID is NOT an insecticide used to “Kill Bugs
Dead” by SC Johnson Company.

21. What RAID is NOT!
RAID is NOT data backup - Data can still
become damaged in a RAID array.
RAID is NOT immune to viruses and other
disasters that could potentially cause data loss.
RAID is NOT an insecticide used to “Kill Bugs
Dead” by SC Johnson Company.

22. Questions?
cpierce@csdurant.com
www.twitter.com/cpiercecs