Is Disk Fragmentation Still A Thing?

There are still benefits, but it’s definitely not for everyone.

If you’ve been around computers for a while, you may remember a time when you would hear people talk about needing to defragment their hard drive, particularly if they used a PC, where there is a built-in utility. With Macs, however, the story is a little different.

Since Mac OS X 10.2, a lot of file defragmentation is handled by the file system, such that files under 20 MB are defragmented automatically. So if you find that your Mac is running slowly, odds are that it’s not actually a result of fragmentation. The exception to this relates to files larger than 20 MB. If you deal with large graphics files, video, or other large-format data, then you may benefit from defragmenting if you use a standard rotational hard drive, and you experience delays when dealing with those larger files.

How to defragment on a Mac

As mentioned above, however, Macs don’t include a built-in defragmentation utility. For this, you’ll need to turn to third party utilities. Three options to consider are iDefrag, Techtool Pro, and Drive Genius. iDefrag does only defragmentation and has more defragmentation options, but is no longer supported after macOS 10.12. Techtool Pro calls defragmentation “optimization,” and offers tools to optimize both whole disks and just files over 20 MB. Drive Genius also includes a Defragment function. With any defragmentation, be sure to make sure your data is backed up first. If unexpected errors, power surges or outages occur during a defragmentation, you may lose data.

Starting in macOS 10.14 Mojave, rotational hard drives join solid state drives in utilizing APFS, Apple’s new file system, and none of the above can defragment drives formatted using APFS.

Defragmenting Solid State Drives

When it comes to defragmenting solid state drives, the simple answer is “don’t.” Solid state drives access all data on a drive at the same speed regardless of physical location on the disk, so there really is no benefit. In fact, accessing fragmented data might actually be faster. You may have noticed that as solid state drives have gotten larger, they have also gotten faster. The reason for this is that manufacturers tend to add capacity by increasing the number of NAND chips on the disk. Reading and writing from more chips increases the speed of those read and write operations, so if your data is spread across multiple chips, it reads and writes faster.

Of course, we should not forget the dangers of attempting to defragment solid state drives, chief of which is reducing longevity. Each write operation adds wear to a solid state drive, which can only write to each sector so many times, so in addition to providing no benefit, defragmenting a solid state drive will actually wear it out that much faster.

As solid state drives become more and more common, the need for defragmenting disks diminishes, but there are some that can still benefit from organizing their large files, and there are still utilities around that are up to the task.