Installation guide

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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.
Formatting (usually known as "making a file system") writes information to the drive, creating or-
der out of the empty space in an unformatted drive.
Figure 25.2. Disk Drive with a File System
As Figure 25.2, “Disk Drive with a File System”, implies, the order imposed by a file system in-
volves some trade-offs:
• A small percentage of the drive's available space is used to store file system-related data
and can be considered as overhead.
• A file system splits the remaining space into small, consistently-sized segments. For Linux,
these segments are known as blocks.
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Given that file systems make things like directories and files possible, these trade-offs are usu-
ally seen as a small price to pay.
It is also worth noting that there is no single, universal file system. As Figure 25.3, “Disk Drive
with a Different File System”, shows, a disk drive may have one of many different file systems
written on it. As you might guess, different file systems tend to be incompatible; that is, an oper-
ating system that supports one file system (or a handful of related file system types) may not
support another. This last statement is not a hard-and-fast rule, however. For example, Red Hat
Enterprise Linux supports a wide variety of file systems (including many commonly used by oth-
er operating systems), making data interchange between different file systems easy.
Figure 25.3. Disk Drive with a Different File System
Of course, writing a file system to disk is only the beginning. The goal of this process is to actu-
ally store and retrieve data. Let us take a look at our drive after some files have been written to
it.
1.1. It is Not What You Write, it is How You Write It
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