User's Manual

Section E.1:Hard Disk Basic Concepts 101
Figure E–2 Disk Drive with a Filesystem
As Figure E–2, Disk Drive with a Filesystem 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.
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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 E–3, Disk Drive with
a Different Filesystem shows, a disk drive may have one of many different filesystems written on it.
As you might guess, different filesystems 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 Linux supports a wide variety
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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.