Defragmentation used to be a big issue: files and folders are always packed on the hard drive where there is space. Over time, the data is scattered more and more, which means that the read / write head of the mechanical hard disk has to work harder. The result: the operating system becomes slow. However, Windows and macOS now usually do the defragmentation completely automatically.
In this tip we explain how to defragment hard disks under Windows.
Defragment Mac hard drive - do you need it?
Defragmenting on the Mac is not necessary
If you are looking for defragmentation software for the Mac, the best you can find today is the iDefrag program. However, this was only supported up to macOS 10.12, and the manufacturer cryptically reports on the website that support has been discontinued. The reason is obvious: On the one hand, most Macs now have SSD hard drives ex works. And on the other hand, the new APFS file system is optimized for these SSDs, which means that hard disk defragmentation is basically no longer necessary..
SSD fragmentation is not a problem
Roughly speaking, mechanical hard disks work in a similar way to a record player: the disk with data rotates, a read / write arm collects the data. This is adjusted mechanically, which always takes a few milliseconds when it is moved to a different location. If a mechanical hard drive is severely fragmented, the arm has to be changed more frequently. As a result, frequent smaller delays add up to a significantly slower overall system. This is not the case with SSDs: there is no arm that has to be driven around, the fast memory banks are all equal and have the same speed. In other words: Anyone who uses a Mac with an SSD, especially the latest macOS, does not have to worry about fragmentation and the resulting speed problems. Incidentally, neither on iOS, i.e. on the iPhone and iPad:Here, too, fixed storage devices with the APFS file system are used.
Why defragmentation is pointless on the Mac
Much more important, however, is the fact that macOS uses the HFS + file system. This has had an internal defragmentation algorithm since macOS 10.3 in 2005: When a file is opened, the file system checks whether it is smaller than 20MB, whether it is currently open or write-protected and whether it is on a contiguous section of the hard drive, i.e. not fragmented . If that is the case, macOS takes this file, collects the individual parts and places them in a contiguous area of the hard drive. In other words: the HFS + file system and therefore macOS defragments itself! Defragmentation as under Windows is therefore not necessary - even with mechanical hard drives, as they are still installed in some entry-level models!