Compaq 108164-003 - ProLiant - 800 White Paper page 25

Note: Within each test
comparison, the total disk
capacity remained constant.
ECG025.0997
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HITE APER
(cont.)
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Multiple Disk Controller Test Results
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In our multiple disk controller tests we found that concurrency coupled with adding disk
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controllers to an environment increases system performance. For instance, Figure 13
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displays a comparison between two tests in a RAID 5 environment. First, we tested
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twelve 4GB drives (11 data, 1 parity) using one controller. Next using two controllers, we
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. . equally split the number of drives (5 data, 1 parity) on each controller, totaling 10 data and
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2 parity drives. Even though we had two drives dedicated to parity in the two controller
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environment, test results still show a significant benefit, yielding a 57% increase in
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system performance.
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20,000,000
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18,000,000
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16,000,000
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14,000,000
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12,000,000
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10,000,000
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8,000,000
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6,000,000
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4,000,000
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2,000,000
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0
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Figure 13: Disk Controller Scaling in a RAID 5 Environment.
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The disk controller scaling tests configured with no fault tolerance or RAID 0, shown in
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Figure 14, receives only a minimum performance gain of 3% between one and two
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controllers. Since we enhanced the disk subsystem and did not see any significant
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improvement, other factors must be limiting our throughput. Upon examination of the
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other subsystems, we found the processors nearly saturated. To remove this bottleneck,
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we would have to use faster processors and rerun the test. Nevertheless, remember that
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changing the disk subsystem enhances performance only if it is the bottleneck. In this
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case, the processors are the bottleneck and not the disk subsystem, so changing the disk
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subsystem provides no benefit towards improving performance.
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25
Disk Controller Scaling (RAID 5)
57%
16 20 24 28 32
Number of Clients
10+2 x 4GB, 2 Ctr
11+1 x 4GB, 1 Ctr
36 40 44 48 52 56 57