Partitioning is the process of dividing the hard disk into subsections, called volumes.
It is an important initial step in preparing a hard disk for use, and is discussed in
detail on this page.
The choice of how the hard disk is partitioned can have a tangible impact on
real-world performance. This is due to several different but related effects that you
should keep in mind when deciding how to partition your drive:
- Cluster Size: The way that the hard disk is partitioned in most cases determines
the cluster size of the partition, which has a performance impact. See this section for details.
- Zone Effects: Modern hard disks use zoned bit recording to allow more data to be
stored on the outer tracks of the hard disk than the inner ones. This directly impacts the
media transfer rate of the disk when reading one zone of the disk as opposed to another; see here for details. Hard disks fill their space
starting from the outer tracks and working inward. This means that if you split a hard
disk into three partitions of equal size, the first partition will have the highest
transfer rate, the second will be lower, and the third lower still. Therefore, you can put
the more important files on the faster partitions if transfer performance is important to
you.
- Seek Confinement: Seek times are
roughly proportional to the linear distance across the face of the platter surfaces that
the actuator must move the read/write heads. Using platters of smaller diameter improves
seek time, all else being equal, and partitioning can have the same net effect. If you
split a drive into multiple partitions, you restrict the read/write heads to a subsection
of the physical disk when seeking, as long as you stay within the same partition. The
tradeoff is that if you do a lot of moving data between partitions, or accessing
multiple partitions simultaneously, you'll force the heads to "jump" back and
forth between two completely different areas of the disk, reducing performance. Some who
truly desire performance over all else will buy a hard disk with double the capacity that
they need, partition it in two pieces and use only the first half! Or use the second half
only for archiving infrequently-used data.
- Defragmentation Time: Larger partitions tend to become full of, well,
more data, obviously.
A larger partition can take much longer to defragment than a
smaller one. Since fragmentation reduces
performance, some people prefer to partition their drives to reduce defragmentation time,
enabling them to do it more frequently.
There are, of course, non-performance issues in partitioning. See this long description of partitioning issues in the file
system section as well.
Next: Cluster Size
