Partitions: Turning One Drive Into Many - Red Hat ENTREPRISE LINUX 5 Installation Manual

26.1.2. Partitions: Turning One Drive Into 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.
Figure 26.5. Disk Drive with Partition Table
Figure 26.5, "Disk Drive with Partition Table"
As
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
type, to flag the partition as being associated with a particular operating system, to indicate that the
partition contains a bootable operating system, or some combination of the three.
By this point, you might be wondering how all this additional complexity is normally used. Refer to
Figure 26.6, "Disk Drive With Single
shows, the partition table is divided into four sections
Partition", for an example.
Partitions: Turning One Drive Into Many
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