Defragging an SSD or Fusion Drive (which is a combination of an SSD and a HDD) can actually be dangerous to the drive and reduce its lifespan.

An SSD uses flash memory to store data rather than spinning mechanical platters. More and more Macs are doing away with Hard Disk Drives and using solid-state drives - SSDs - for data storage. HFC still does a very good job of keeping the files unfragmented, but as time passes this type of user may see a performance hit. Generally, these people are creatives who use a lot of big files in their work.

The exception is for those Mac users who have hundreds or thousands of very large files (usually audio or video files) larger than 1GB in size. HFC works very well for most users and as a result, most users should never need to defrag a Mac hard drive. Think of HFC as constantly performing defragmentation on hard disk drives, ensuring that the HDD is always as optimized as possible for reading and writing data. Since the days of Mac OS X “Panther” (which shipped in 2003), Mac OS X and its successor macOS have used something called Hot File Adaptive Clustering (HFC) to automatically defragment files. Why Macs Usually Don’t Need to be Defragged The result? Faster loading of apps and data. This slows down operation.ĭefragmentation reads the files on the HDD platters, then rewrites them on the platters so single files are written contiguously and the drive head doesn’t need to move back and forth as much. As a result, those files are stored in locations all over the drive platters and the moving read/write head must travel the complete width of the platter to load files. Data can’t automatically migrate itself to the outer edges of the platters to fill in available space, so after many read/write cycles have been completed, there are gaps where large files cannot be written. New data is generally written to the outside of the platters, with the read/write heads moving in toward the center as more data is stored. HDDs use a magnetic read/write head to access rotating round platters that usually spin at either 5,400 or 7,200 revolutions per minute (see image above right). In this article, we’ll discuss why defragging Mac HDDs is usually unnecessary and how to do it if you’re one of the few users who may actually benefit from the process.ĭefragging is a slang term for “defragmentation”, which is the process of organizing files on a HDD to optimize how it accesses those files. Like all computers, Macs tend to slow down a bit after a few years of usage, and those readers who are new to the Mac might think that the old Windows solution of “defragging the hard disk drive” (HDD) might help. Macs are more popular than ever, thanks to a “halo effect” from buyers of iPhones and iPads who decide to make the switch from Windows to macOS.

Os x defragment disk