Christopher Duff
LIS506LECOA1
1.
How many 4.7 GB write-once DVD-R disks would you need to buy to
back up a full 500 GB hard drive once?
500 GB
---------------------- = 106.38 = 107 disks
4.7 GB per disk
At $.30 per disk, how much would a full backup cost?
107 disks x .30 = $32.10
At 10 minutes per DVD-R disk, how long would a full backup take?
107 disks x 10 minutes = 1070 minutes = 17 hours, 50 minutes
Christopher Duff
LIS506LECOA1
2.
Would all of this data fit on the 500 GB hard drive?
Title:
Control number:
Call number:
Publisher:
Publication year:
Current status:
Purchase price:
300 characters
10 characters
50 characters
100 characters
4 characters
2 characters
one 4-byte number
Total: 470 bytes per print volume
Library data: 470 bytes x 3.8 million print volumes = 1.786 billion bytes
Hard drive capacity: 500 GB = 500 billion gigabytes
500 GB > 1.786 GB
Yes, it fits!
What fraction of the hard drive would this fill?
1.786 GB
------------ = .003572 = .3572%
500 GB
Not very much at all!
Used space
Available space
Christopher Duff
LIS506LECOA1
3.
How long would it take to get all materials published in 2012?
If the computer accesses the data in random order and does not know in advance how many
volumes have a publication date of 2012, then it must check every single one of the 3.8 million
volumes. (On the other hand, if it knew in advance that there were exactly 32,230 volumes
from 2012, it could stop searching as soon as it randomly accessed all 32,230 of them. We
would be unable to predict exactly how long this would take, though we could estimate both a
minimum and a maximum access time.)
However, given that the computer must check each of the 3.8 million volumes:
3.8 million volumes x 10 ms access time each
OR
3.8 million x .01 seconds = 38,000 seconds = 633.333 minutes = ~ 10.5 hours
Christopher Duff
LIS506LECOA1
4.
How long would it take the 2.6 GHz processor to perform 3.8 million
comparisons if it can perform one comparison instruction for every
two clock cycles?
Our processor has two CPUs:
CPU 1:
2.6 billion comparisons every 2 clock cycles
OR
1.3 billion comparisons per second
CPU 2:
2.6 billion comparisons every 2 clock cycles
OR
1.3 billion comparisons per second
Total: 2.6 billion comparisons per second
3.8 million comparisons
---------------------------------------------- = .00146 seconds = 1.46 ms
2.6 billion comparisons per second