Archive for October 21st, 2016

by Tom Nelson

Question: I’m a Windows user who recently made the change to Apple and the Macintosh. I’m used to routinely defragmenting my hard drive in order to ensure top performance by my computer. I don’t see any way to defragment my Mac’s hard drive. Do I need to be concerned about this?


Screen shot © Coyote Moon, Inc.

Answer: Apple supplies a handy application for working with hard drives called Disk Utility.

If you open up Disk Utility, you’ll notice that it doesn’t include a tool for defragmenting any of the drives connected to your Mac. The reason for this perceived oversight is that a Mac running any version of OS X later than 10.2 does not need to be defragmented. OS X as well as macOS have their own built-in safeguards that prevent files from becoming fragmented in the first place.

  • The Mac’s HFS+ file system tries not to use recently freed file space on a disk. Instead, it looks for larger free areas already present on the drive, thereby avoiding fragmenting files just to fit them into available space.
  • The Mac OS dynamically gathers groups of small files and combines them into larger areas on your disk automatically. The process of writing the files to a new larger location defragments all of the files in the group.
  • OS X and MacOS implement Hot File Adaptive Clustering, which monitors frequently-accessed files that do not get changed (read only), and then moves these often-accessed files to a special hot zone on the startup drive. In the process of moving these files, OS X defragments them, and then stores them in the area of the drive that has the fastest access.
  • When you open a file, the Mac checks to see if it is highly fragmented (more than 8 fragments). If it is, the operating system will automatically defragment the file.

The result of all these safeguards is that the Mac rarely, if ever, needs to have its disk space defragmented. The only real exception to this is when your hard drive has less than 10 percent free space.

At that point, the Mac operating system is unable to perform its automatic defragmentation routines, and you should consider either removing files or expanding your disk storage size.

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