User's Manual

Drive Arrays and Fault Tolerance
D-8 HP Smart Array 641/642 Controller User Guide
HP CONFIDENTIAL
Writer: John Turner File Name: l-appd drive arrays & fault tolerance
Codename: darkmatter -antimatter Part Number: 309311-001 Last Saved On: 11/6/02 4:34 PM
S1
S2
S3
S4
B1
B3
P5,6
P3,4
P1,2
P7,8
B7
B2
B5
B8
B4
B6
Figure D-7: Distributed data guarding, showing parity
information (Px,y)
This configuration is useful when cost, performance, and data availability are equally
important.
Advantages
• High read performance
• No loss of data if one physical drive fails
• More drive capacity usable than with RAID 1+0—parity information requires
only the storage space equivalent to one physical drive
Disadvantages
• Relatively low write performance
• Loss of data if a second drive fails before data from the first failed drive is rebuilt