HP 226593-B21 Smart Array 5i Plus Controller and Battery Backed Write Cache En - Page 84

drive array, array., C-4.

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Drive Arrays and Fault Tolerance S1 B1 B2 B3 S2 B4 B5 B6 S3 B7 B8 B9 S4 B10 B11 B12 Figure C-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 simply array. Since 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 (see Figure C-4). Compaq Smart Array 5i Plus Controller and Battery Backed Write Cache Enabler User Guide C-3

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Drive Arrays and Fault Tolerance
Compaq Smart Array 5i Plus Controller and Battery Backed Write Cache Enabler User Guide
C-3
S1
S2
S3
S4
B1
B4
B7
B2
B5
B8
B11
B10
B12
B6
B3
B9
Figure C-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
simply
array.
Since 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 (see
Figure C-4).