Originally featured in Tech Tails issue #711.
One of the most popular questions I’m asked as a service technician is, “Should I have a utility to check up on my Mac?” The short answer is, yes, you probably should. While there are hundreds of utilities out there, I’m going to focus on the one I use the most, Drive Genius 2 by ProSoft. That’s not to say there are not alternatives that may be just as great, but Drive Genius has been a solid utility that I’ve used since it was first released.
Drive Genius is a nice solid tool because it incorporates utilities to check the hardware of the hard drive as well as the software. As with all utilities, it’s certainly possible to get false-negatives, but this could definitely help when trying to decide if the issue you’re experiencing is hard drive failure or software corruption. It gives you tools for surface scans, software verification and repair, integrity checks and even defragmentation (which is rarely necessary on a Mac).
Generally, if we get a machine in the shop and we suspect the hard drive is failing but it’s not as obvious as a drive that’s clicking repeatedly and won’t mount, we start running a surface scan on the drive. A surface scan checks for bad blocks. Some technicians believe that all drives have bad blocks; I respectfully disagree with that assertion. While it’s true that all drives may physically have some bad blocks, those blocks should be identified by software while formatting the drive and they are not used in the volume structure and should not show up in a surface scan.
To demonstrate that theory, if you run surface scans on 10 “healthy” formatted drives, there should be no bad blocks identified; that’s what we see in the shop. If bad blocks do show up that means something has gone wrong since formatting the drive and that is usually that the hard drive is physically failing. If you only end up with one or two bad blocks you can take the risk and reformat the drive and continue on with your day.
However, it’s recommended to check up on the drive from time to time because if more bad blocks show up, the drive should be replaced. If a surface scan is run and several bad blocks appear, don’t hesitate to replace the drive.
A drive displaying bad blocks is not the only type of hard drive failure. I’ve written before about a great tool by DriveSavers that demonstrates several ways a drive can fail. That means that a surface scan is not the end-all-be-all hard drive test.
If a drive that we suspect is failing passes a surface scan, the next step is usually to run an integrity check. The integrity check measures read/write speeds of the drive and compares it to a “normal” range. If the drive is performing drastically out of the normal range, it’s indicative that it’s time to replace the drive.
Aside from physical hard drive failure, often times drives that display symptoms of failure (like slowness and constant spinning beach balls) are actually a result of software corruption and not physical drive failure. While you can certainly verify and repair your hard drive’s volume structure by using Disk Utility, Drive Genius includes a “rebuild” function along with verify and repair.
Rebuild is particularly useful when the repair function is not up to snuff. I would say this is the #1 tool most home users would use. It is important to point out that not all rebuild utilities are made equal. While I love that Drive Genius includes that feature, and I use it regularly, Disk Warrior still wins in my book for its phenomenal ability to rebuild corrupt volumes.
The final feature you may wish to play with is defragmentation. Basically, when the drive head writes data to a hard disk it rarely puts things in the same physical place on the drive. Since data is constantly being erased and overridden there are pockets of space all over the drive so the drive head finds these pockets and splits the data up among them; this is called “fragmentation.” Over time, if files are badly fragmented it could take longer for the files to be retrieved so you might notice your machine is slowing down.
On a Mac, some defragmentation happens automatically as part of the boot up process, so most Mac users find they need to defrag much less often than PC users. Some Apple technicians say it’s not necessary to defrag at all, and I’m honestly close to that train of thought. However, I have found it’s helped in some situations; especially if it’s a large drive and has had very large chunks of data erased and re-written. I will say that I would not jump right to this step.
It’s also incredibly important to back up your data before defragmentation. While that should be an obvious step before running any major utility, I find it’s particularly imperative when defragmenting as I can vouch from personal experience that occasionally defragmentation can end up erasing or misplacing files and if those are system files you might end up with a machine that boots to a flashing question mark or to a kernel panic. That’s no fun!
If you don’t own a drive utility for your Mac, I encourage you to invest in one. While Drive Genius is my personal favorite, there are certainly others out there (including Onyx , a favorite of our readers) that you can try. Just do yourself a favor and be sure to back up your data first! Enjoy!