Installation guide

As with most computer-related technologies, disk drives changed over time after their introduction. In
particular, they got bigger. Not larger in physical size, but bigger in their capacity to store
information. And, this additional capacity drove a fundamental change in the way disk drives were
used.
26.1.2. Part it ions: T urning One Drive Int o Many
As disk drive capacities soared, some people began to wonder if having all of that formatted space in
one big chunk was such a great idea. This line of thinking was driven by several issues, some
philosophical, some technical. On the philosophical side, above a certain size, it seemed that the
additional space provided by a larger drive created more clutter. On the technical side, some file
systems were never designed to support anything above a certain capacity. Or the file systems could
support larger drives with a greater capacity, but the overhead imposed by the file system to track
files became excessive.
The solution to this problem was to divide disks into partitions. Each partition can be accessed as if it
was a separate disk. This is done through the addition of a partition table.
Note
While the diagrams in this chapter show the partition table as being separate from the actual
disk drive, this is not entirely accurate. In reality, the partition table is stored at the very start of
the disk, before any file system or user data. But for clarity, they are separate in our diagrams.
Fig u re 26 .5. Disk Drive wit h Part it io n T ab le
As Figure 26.5, “ Disk Drive with Partition Table” shows, the partition table is divided into four
sections or four primary partitions. A primary partition is a partition on a hard drive that can contain
only one logical drive (or section). Each section can hold the information necessary to define a
single partition, meaning that the partition table can define no more than four partitions.
Each partition table entry contains several important characteristics of the partition:
The points on the disk where the partition starts and ends
Whether the partition is "active"
The partition's type
Let us take a closer look at each of these characteristics. The starting and ending points actually
define the partition's size and location on the disk. The "active" flag is used by some operating
systems' boot loaders. In other words, the operating system in the partition that is marked "active" is
booted.
The partition's type can be a bit confusing. The type is a number that identifies the partition's
anticipated usage. If that statement sounds a bit vague, that is because the meaning of the partition
type is a bit vague. Some operating systems use the partition type to denote a specific file system
Red Hat Ent erprise Linux 5 Inst allat ion G uide
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