Drive Arrays and Fault Tolerance

S1

B1

B2

P1,2

 

S2

B3

P3,4

B4

 

S3

P5,6

B5

B6

 

S4

B7

B8

P7,8

 

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

D-8

HP Smart Array 641/642 Controller User Guide