recording density 512K bitscm track density 128K trackscm average track

# Recording density 512k bitscm track density 128k

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recording density 512K bits/cm track density 128K tracks/cm average track circumference 4 cm usable radial disk size 2 cm maximum track circumference 8 cm rotation speed 128 revs/sec sector size 512 bytes number of platters 2 Part A (15 points) Complete the following disk summary. Use power of two approximation; but express the final answer in decimal (e.g., 16 instead of 2 4 ). Show work. avg. track capacity 512 Kbits/cm x 4 cm / 8 bits/byte = 256 Kbytes avg. cylinder capacity 256 Kbytes/track x 4 tracks/cylinder = 1 Mbytes surface capacity (1 head) 128Ktracks/cm x 2cm x 256 Kbytes = 64 Gbytes total disk capacity 64 Gbytes/ surface x 4 surfaces = 256 Gbytes max data transfer rate 512 Kbits/cm x 8 cm x 128 rev/sec = 512 Mbits/sec Part B (15 points) The total time to load a file from disk is the sum of three parameters: cylinder seek time, rotational access latency, and data transfer time. Listed below are several design alternatives along with key disk specs. For each item, list " + " if the parameter increases, " - " if the parameter decreases, and " = " if the parameters is unchanged as a result. Note: " + " and " - " should not be used to mean "better" and "worse" respectively; Often a decreasing value means faster (and better). Ignore the grayed box. proposed design improvement storage capacity cylinder seek time rotational latency data transfer time increase # sectors per track + - = - increase tracks / surface + = = = add more platters + - = = spin disk faster = = - - 6

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• Fall '08
• Staff
• hash function, access time, Seek time, character string