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Figure 9.31
Synchronized drives; 16 drives clustered as four groups (m = 4) of
four synchronized (1, s) drives, where s = 4, i.e., 4 ´ (1,4). |
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Figure 9.32
Distributed drives (dd): striping a file across q distributed drives. |
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E(f) is the expected file size (in blocks) of a file with block probability distribution function f. |
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E(f/q) is the expected number of blocks on each of q disks when a file with block probability distribution f is striped (dd) across the disks. |
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E(fd/q) is the expected number of disks to be accessed when a file of block probability distribution f is striped (dd) over q disks. |
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If a system consists of an ensemble of (q,1) distributed disks, then the file distribution must be considered. (See Figure 9.32.) Define E(fd/q) as the expected number of disks to access a file (out of q) with a block probability distribution f: |
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Figure 9.33
E(f), E(f/q), and E(fd/q). |
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