1.Given the following characteristics for a magnetic tape using linear recording

Question

1.Given the following characteristics for a magnetic tape using linear recording as described in this chapter:

Density = 1600 bpi

Speed = 1500 inches/second         

Size = 2400 feet

Start/stop time = 4 ms                    

Number of records to be stored = 200,000 records

Size of each record = 160 bytes

Block size = 10 logical records

IRG = 0.5 inch

Find the following:

a.              Number of blocks needed
b.              Size of the block in bytes
c.              Time required to read one block
d.              Time required to write all of the blocks.
e.              Amount of tape used for data only, in inches
f.               Total amount of tape used (data + IRGs), in inches

Explanation / Answer

a. Blocks needed = 200,000 rec / 10 rec/block = 20,000 blocks

b. Size of block in bytes = 160 bytes/rec * 10 rec/block = 1600 bytes/block]

c. Time to read or write one block (assuming tape is at speed):
-- data time = 1600 bytes/block / 1600 bytes/in / 1500 in/sec = 0.00067 sec/block
-- ibg time = 0.5 in/block / 1500 in/sec = 0.00033 sec/block
-- total = 0.00067 + 0.00033 = 0.0010 sec/block

d. Total time = 20,000 blocks * 0.0010 sec/block = 20.06 sec

e. Data length = 20,000 blocks * 0.00067 sec/block * 1500 in/sec = 20,100 in

f. Total length = 20.06 sec * 1500 in/sec = 30,090 in (2500 feet - won't fit 2400 foot tape)

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