Generalized Optimal Response Time Retrieval of Replicated Data from Storage Arrays

Disk Parameters

Speed of a disk is defined as the average time it takes to retrieve a single data block from that disks. In our experiments, we use the disk specifications given in Table 1.


Table 1: Disk Specifications
Producer Model Type RPM Speed (ms)
Seagate Barracuda HDD 7.2K 13.2
WD Raptor HDD 10K 8.3
Seagate Cheetah HDD 15K 6.1
OCZ Vertex SSD - 0.5
Intel X25-E SSD - 0.2

Experiments

All the experiments conducted are summarized in Table 2. Delay and initial load values are given in milliseconds. R(2,10,2) means that a number among the set 2, 4, 6, 8, and 10 is chosen randomly. If the system is homogeneous, the properties of the cheetah disk is used for all the disks in the system. If the system is heterogeneous, then the disks are chosen randomly among the disk group indicated in the table. Disk groups can be HDDs, SSDs, or HDDs+SSDs.


Table 2: Experiment Parameters
Experiment Number of Disk Site 1 Site 2
Number Sites Properties Disks Delays Loads Disks Delays Loads
1 1 homogeneous cheetah 0 0 - - -
2 1 heterogeneous ssd 0 0 - - -
3 1 heterogeneous hdd 0 0 - - -
4 1 heterogeneous ssd+hdd 0 0 - - -
5 1 heterogeneous ssd+hdd R(2,10,2) R(2,10,2) - - -
6 2 homogeneous cheetah 0 0 cheetah 0 0
7 2 homogeneous cheetah 0 0 cheetah 0 20
8 2 homogeneous cheetah 0 5 cheetah 0 15
9 2 homogeneous cheetah 0 10 cheetah 0 10
10 2 homogeneous cheetah 0 15 cheetah 0 5
11 2 homogeneous cheetah 0 20 cheetah 0 0
12 2 homogeneous cheetah 0 0 cheetah 20 0
13 2 homogeneous cheetah 5 0 cheetah 15 0
14 2 homogeneous cheetah 10 0 cheetah 10 0
15 2 homogeneous cheetah 15 0 cheetah 5 0
16 2 homogeneous cheetah 20 0 cheetah 0 0
17 2 heterogeneous ssd 0 0 hdd 0 0
17 2 heterogeneous hdd 0 0 ssd 0 0
19 2 heterogeneous ssd+hdd 0 0 ssd+hdd 0 0
20 2 heterogeneous ssd+hdd R(2,10,2) R(2,10,2) ssd+hdd R(2,10,2) R(2,10,2)

Results

Results of the experiments defined in Table 2 is provided in Table 3.


Table 3: Experimental Results
Experiment
 All Results
Experiment 1
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Experiment 2
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Experiment 3
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Experiment 4
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Experiment 5
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Experiment 6
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Experiment 7
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Experiment 8
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Experiment 9
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Experiment 10
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Experiment 11
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Experiment 12
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Experiment 13
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Experiment 14
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Experiment 15
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Experiment 16
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Experiment 17
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Experiment 18
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Experiment 19
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Experiment 20
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