Appendix E. An Introduction to Disk Partitions

107

Figure E 4. Disk Drive with Data Written to It

As Figure E 4, shows, 14 of the previously empty blocks are now holding data. However, by simply

looking at this picture, we cannot determine exactly how many files reside on this drive. There may

be as few as one or as many as 14 files, 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 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.

E.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, we will keep it separate in our diagrams.

Figure E 5. Disk Drive with Partition Table