Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Przewodnik Instalacji Pobierz pdf (Strona 239)

Figure 25.4. Disk Drive with Data Written to It

As Figure 25.4, “Disk Drive with Data Written to It”, shows, some of the previously-empty blocks

are now holding data. However, by just looking at this picture, we cannot determine exactly how

many files reside on this drive. There may only be one file or many, as all files use at least one

block and some files use multiple blocks. Another important point to note is that the used blocks

do not have to form a contiguous region; used and unused blocks may be interspersed. This is

known as fragmentation. Fragmentation can play a part when attempting to resize an existing

partition.

As with most computer-related technologies, disk drives changed over time after their introduc-

tion. 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.

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 is-

sues, 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 tech-

nical 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 im-

posed 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 clar-

ity, they are separate in our diagrams.

1.2. Partitions: Turning One Drive Into Many

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Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Przewodnik Instalacji Strona 239