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Include the appropriate number of physical drives in the arrays to create logical storage elements
of desired sizes.
Arrays
See
Figure
2. With an array controller installed in the system, the capacity of several physical drives
(P1–P3) can be logically combined into one or more logical units (L1) called arrays. When this is
done, the read/write heads of all the constituent physical drives are active simultaneously, dramatically
reducing the overall time required for data transfer.
NOTE:
Depending on the storage server model, array configuration may not be possible or necessary.
P1
Figure 2 Configuring arrays from physical drives
Because the read/write heads are simultaneously active, the same amount of data is written to each
drive during any given time interval. Each unit of data is termed a block. The blocks form a set of
data stripes over all the hard drives in an array, as shown in
S1
B1
S2
B4
S3
B7
S4
B10
Figure 3 RAID 0 (data striping) (S1-S4) of data blocks (B1-B12)
For data in the array to be readable, the data block sequence within each stripe must be the same.
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 hard drive in a given array contains the
same number of data blocks.
NOTE:
If one hard drive has a larger capacity than other hard drives in the same array, the extra capacity is
wasted because it cannot be used by the array.
L1
P2
P3
gl0042
B2
B3
B6
B5
B8
B9
B11
B12
gl0043
HP ProLiant SB460c SAN Gateway Storage Server
Figure
3.
17
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Troubleshooting
