Information Technology Reference
In-Depth Information
Chapter 11
File Systems:
Introduction and Overview
Memory is the treasury and guardian of all things.
{MarcusTulliusCicero
Computers must be able to reliably store data. Individuals store family
photos, music files, and email folders; programmers store design documents and
source files; oce workers store spreadsheets, text documents, and presentation
slides; and businesses store inventory, orders, and billing records. In fact, for a
computer to work at all, it needs to be able to store programs to run and the
operating system, itself.
For all of these cases, users demand a lot from their storage systems:
Reliability. A user's data should be safely stored even if a machine's
power is turned of or its operating system crashes. In fact, much of this
data is so important that users expect and need the data to survive even
if the devices used to store it are damaged. For example, many modern
storage systems continue to work even if one of the magnetic disks storing
the data malfunctions or even if a data center housing some of the system's
servers burns down!
Large capacity and low cost. Users and companies store enormous
amount of data, so they want to be able to buy high capacity storage
for a low cost. For example, it takes about 350 MB to store an hour of
CD-quality losslessly encoded music, 4 GB to store an hour-long high-
definition home video, and about 1 GB to store 300 digital photos.
Binary
Decimal
Unit
Bytes
Bytes
2
20
10
6
MB
As a
2
30
10
9
GB
2
40
10
12
TB
2
50
10
15
PB
327
2
60
10
18
EB
