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7 Cards in this Set
- Front
- Back
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(1/2) List two differences in access between Disk vs. Memory?
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Access:
-memory location are accessible individually -data on disk can only be accessed one chunk at a time (block) |
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(2/2) List two differences in naming between Disk vs. Memory?
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Naming:
• variables are accessed using their address. • data on disk is normally accessed through a file name • the OS translates the name and offset into a logical block number • the disk controller maps that number to the location on disk |
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What are the three factors that affect retrieving data from a hard disk?
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Seek Time, Rotational Latency, Average Transfer Time
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Define: Seek Time
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Time to position the arm on the right track
formula = ~9ms |
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Define: Rotational Latency
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Time to position head at the right sector
formula = 1/2 * 1/ RPM * 60secs |
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Define: Average Transfer Time
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Time to transfer a sector
formula = 1/ RPM * 1/<avg sectors per track> * 60secs |
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What is the access time of a disk with 15,000 RPM, 10ms avg seek time and 500 sectors/track?
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Access Time = Seek Time + Rotational Latency + Average Transfer Time =
10ms * 1/1000secs] + [ 1/2 * 1 / 15,000RPM * 60secs ] + [ 1/15,000RPM * 1/500 sectors/track * 60secs] = 0.012008ms(??) |
