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Volume Free Space

A relevant performance consideration that most people don't pay attention to is how full their hard disk is. The amount of free space on a hard disk affects the performance of the drive, for most of the same reasons that partitioning affects it:

• The more data on the volume, the more the data is spread out over the disk, reducing positioning performance;
• A disk that is more full forces new files to the inner tracks of the disk where transfer performance is reduced; and
• Drives that are full both take longer to defragment and tend to be more fragmented in the first place.

The "Peter Principle" of hard disks is that the amount of junk put on a hard disk expands to fill the available space, regardless of the size of the hard disk. Imagine what PC users 10 years ago would have thought about people with 6 GB hard disks needing an upgrade because their "disk is too full!" I had the personal experience the other day of surprisingly discovering that a 15 GB hard disk volume I had just installed was down to 2 GB free! Most people don't clean out their disks until they have to. :^)

The bottom line though is clear: the more "stuff" you put on that humongous hard disk you just bought, the more you will slow it down. :^) Don't fill your drive with clutter just because you have the space. Regularly go through your hard disk to get rid of files you don't need; if you think you will need them "at some point" then archive them to a tape, CD-R disk or other removable medium.

Another impact of this is that you cannot reliably compare performance benchmarks even on the same disk in the same system if you change the amount of data on the drive between runs. All drives will tend to show a reduction in performance as you fill them up, so benchmarking should always be done on empty drives to eliminate this variable.

Next: Fragmentation

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