HP Integrity rx4640 Server - Manual (Page 77)

Drive Arrays and Fault Tolerance
S1
S2
S3
S4
B1
B4
B7
B2
B5
B8
B11 B10 B12
B6
B3
B9
Figure D-3: Data striping (S1-S4) of data blocks B1-B12
For data in the logical drive to be readable, the data block sequence must be the same
in every stripe. This sequencing process is performed by the array controller, which
sends the data blocks to the drive write heads in the correct order.
A natural consequence of the striping process is that each physical drive in a given
logical drive will contain the same amount of data. If one physical drive has a larger
capacity than other physical drives in the same logical drive, the extra capacity is
wasted because it cannot be used by the logical drive.
The group of physical drives containing the logical drive is called a drive array (or
just array). Because all the physical drives in an array are commonly configured into
just one logical drive, the term array is also often used as a synonym for logical drive.
However, an array can contain several logical drives, each of a different size (refer to
Figure D-4).
HP Smart Array 5300 Controller User Guide D-3
HP CONFIDENTIAL
Writer: Kimberly Koch File Name: m-appd drive arrays and fault tolerance.doc
Codename: SilverHammer Part Number: 135606-006 Last Saved On: 3/13/03 2:02 PM