With sales of Macs reaching an all-time high, there are a lot of new users who are coming over from the world of Windows PCs. After a few years, all computers seem to slow down somewhat, and new Mac owners might think back to the solution that they turned to on those Windows computers — defragging the hard disk drive (HDD). Well, they won’t find any command or utility to let them do that on a Mac. In this Tech 101, I’ll talk about why defragging is largely unnecessary on a Mac and how to do it if you’re one of the users who may need to defrag a HDD.
Note: SSDs do not use a spinning platter to store data; instead, data is stored and accessed from flash memory. Attempting to defrag an SSD or Fusion Drive is actually dangerous to the drive, as it can reduce its lifespan. So never defrag a SSD, OK? For more background on the difference between SSDs and HDDs, check out this recent Tech 101 post on the Rocket Yard.
What is defragging?
Defragging is short for “defragmentation”, the process of organizing the files on a hard disk drive to optimize how it reads and writes those files. HDDs use a magnetic read/write head to access a fast, rotating round platter, typically spinning at 5,400 or 7,200 revolutions per minute. As you’d expect, although the platter is rotating at a fixed rate, the outside edge of the platter is moving faster than the inside edge. As a result, new data is generally written on the outside of the platter, moving in towards the center as more data is stored over the years.
However, the data can’t automatically migrate itself to the outer edges of the platter to fill in available space, so after a lot of reads and writes have been performed, there are small gaps where big files can’t be written, so they are stored in places all over the drive platter. Since the moving read/write head has to travel all over the width of the platter to load files or applications, the entire system seems to slow down.
Defragmentation is the process of reading files, then rewriting them so that single files are written on the spinning platter in such a way that the drive head doesn’t need to move back and forth. A file that may have been splattered all over the platter is placed in a contiguous band, so loading apps and files speeds up.
Why Macs usually don’t need defragging
There’s a reason why Macs typically don’t need defragging — the Mac OS X file system is designed differently than Microsoft’s, and it automatically defragments files. Since OS X 10.3 “Panther”, the file system has used something called Hot File Adaptive Clustering (HFC) to perform that process.
You can think of HFC as constantly performing defragmentation, assuring that the HDD is as optimized as possible for reading and writing data. For most of us, HFC performs perfectly and you may never need to defrag a Mac’s hard drive.
There is an exception to most every rule, and in this case it comes in when people have hundreds or thousands of videos, audio files, or multimedia files that are larger than about 1GB in size. Those people are generally creatives who use big files as their stock in trade. Even then, HFC usually does a pretty good job of keeping things under control, but as time goes by these users may see the performance of their Macs suffer.
What if I do need to defrag?
Since there’s no defragmentation utility built into OS X, how would a creative be able to defrag a large HDD filled with big files? About the only — and best — way that we can recommend doing this is using Drive Genius 4 from Prosoft. This app is used by Apple employees at the Genius Bar when someone comes in with an extremely sluggish Mac that fits the criteria for defragging; in other words, the user has a lot of huge files stored on the HDD.
Drive Genius 4 is not a one-trick pony. It comes with a tool that lets you create a secondary drive so that you can defrag and otherwise optimize your main hard drive, can find and eliminate duplicate files, does secure erasure of drives, and lets you clone a drive if necessary.
What else can I do if my Mac is running slowly?
Sometimes it’s not your HDD that’s having problems. If you have a lot of applications running at the same time and you’re not using them all, consider quitting those apps that you don’t need. You can tell which apps are running by the dot below them on the Dock, and quitting them is as simple as right-clicking on those app icons and selecting Quit.
One issue I’ve personally seen with a lot of Mac users is that they have a large number of apps that launch at startup. Some of these run in background and are only visible in the menubar, so it’s hard to determine if they’re even running. You can stop those apps from loading at startup by opening System Preferences, clicking on Users & Groups, then clicking the Login Items tab. To remove an unused app that loads during startup, click on it to select it, then click on the minus sign ( – ) button below (see image below).
There are some other reasons your Mac might be running slowly — there’s too much data on your HDD or your Mac doesn’t have enough RAM (memory). If you have less than about 10 percent of your HDD space free, your Mac may struggle finding the swap space that it needs when the data and apps being used overwhelm its memory.
Three solutions are possible here:
- Delete unnecessary or out-of-date files from your Mac
- Install a larger HDD
- Install more RAM
The first solution is usually quite easy, as you may find apps that you don’t use, duplicate files, or large files that can be moved to an external disk drive for archival purposes. Once again, Drive Genius 4 is a great solution for finding and removing duplicates.
As for the number two and three items on the list… well, you’ve come to the right place. OWC is the leader in providing do-it-yourself hard disk drive and memory upgrades, complete with instructional videos that show precisely how to go through the process. Check out our highly-acclaimed video series here: eshop.macsales.com/installvideos/