Red Hat ENTERPRISE LINUX WS 2.1 -, Installation Manual

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78 Appendix D. An Introduction to Disk Partitions
D.1.1. It is Not What You Write, it is How You Write It
Experienced computer users probably got this one on the first try. We need to format the drive. For-
matting (usually known as "making a filesystem ") writes information to the drive, creating order out
of the empty space in an unformatted drive.
Figure D-2. Disk Drive with a Filesystem
As Figure D-2, implies, the order imposed by a filesystem involves some trade-offs:
•
A small percentage of the drive’s available space is used to store filesystem-related data and can be
considered as overhead.
•
A filesystem splits the remaining space into small, consistently-sized segments. For Linux, these
segments are known as blocks .
1
Given that filesystems make things like directories and files possible, these tradeoffs are usually seen
as a small price to pay.
It is also worth noting that there is no single, universal filesystem. As Figure D-3, shows, a disk
drive may have one of many different filesystems written on it. As you might guess, different filesys-
tems tend to be incompatible; that is, an operating system that supports one filesystem (or a handful
of related filesystem types) may not support another. This last statement is not a hard-and-fast rule,
however. For example, Red Hat Enterprise Linux WS supports a wide variety of filesystems (includ-
ing many commonly used by other operating systems), making data interchange between different
filesystems easy.
1. Blocks really are consistently sized, unlike our illustrations. Keep in mind, also, that an average disk drive
contains thousands of blocks. But for the purposes of this discussion, please ignore these minor discrepancies.