Do I Need to Defrag my Hard Drive?

Defragmentation refers to the process of reorganising separate fragments of related data on a computer disk into the smallest number of contiguous regions, or fragments.

If your computer or laptop stores data on a hard disk drive (HDD), then defragmentation can be advantageous, and will improve its speeds. Electromagnetic HDDs store data in chunks, known as sectors, and a single file could be broken up across multiple sectors. In order to read a file, your hard drive’s read/write heads have to move across the platters to access the data. If a file is fragmented across multiple sectors, it will take longer for the drive to read it.

Fragmentation occurs when a single file has been broken into multiple pieces. When a file system is first initialised, it is essentially one contiguous block of empty space, and the file system can place newly-created files anywhere, in a near-optimal manner. Over time, as existing files are deleted, fragmentation occurs, and new data is placed into the gaps left. Defragmentation rearranges files so they are stored on sequential sectors of the disk, meaning the heads have less work to do to access the data, increasing read speeds.

If you imagine a hard drive partition that has had data written to it and subsequently deleted over many weeks, months or years, it’s not difficult to see how this can lead to decreased speeds. Beginning with Windows 7, PCs actually defrag your hard drive automatically, so you don’t have to concern yourself with it. If you’re using an older Windows operating system, you can manually defrag your hard drive by right-clicking on your local drive, pressing Properties, then Defragment Now under the Tools tab; an easier solution would be to upgrade to a newer OS.

But do solid-state drives (SSDs) need defragmenting? The short answer is no. SSDs are far faster than HDDs, owing to their lack of moving parts. By storing files on NAND flash chips rather than spinning magnetic platters, data is able to be accessed at a fraction of the speed. With no moving parts, there is little use in defragmenting your SSD. In fact, it could be damaging; SSDs have a limited number of write cycles they can withstand.