Support Blog

What are Volume Structures?

Now that most of us have GPS enabled devices in our pockets, it is (mostly) straightforward to find our way when we're out on the road. When it comes to your hard drive, macOS needs its own GPS to find where your files are located when you need them. This GPS, or map, is how you can think of your drive's volume structures. When the map is damaged, your system loses its way and may be unable to navigate to your important files.

Catalina Drive Map

For most Mac drives, volume structures come in one of two "flavors," Mac OS Extended or APFS. If you are using macOS High Sierra or later, your startup drive uses the newer APFS. While APFS adds new features to better support the solid state drives used in almost all modern Macs, Mac OS Extended can still be found on many external storage drives.

Read more: What are Volume Structures?

Is your life raft ready?

Many of us will eventually experience that sinking feeling, a never-ending spinning beachball. Even worse, when testing reveals an error in the Volume Structures test. Making repairs to your startup disk requires starting up from a separate disk, which exactly the scenario that an eDrive or Protogo device is designed to fill. If, at this point, you have an eDrive or Protogo device, you will be well situated to get your Mac back up and running. You'll have a life raft.

eDrive Protogo

If an eDrive or Protogo device isn't already available, you can end up caught in a catch-22. There are times when creating an eDrive or Protogo device fails because the basis for that device - your internal hard drive - is unable to copy the necessary files. So it's especially important to be prepared and create your eDrive or Protogo device in advance of hard drive problems.

Creating an eDrive starts with the eDrive tool. Simply select the destination device (an external drive is the better option if using Mojave or later), and click create eDrive. Techtool Pro will add a new partition to the drive, and then copy the necessary components to make a valid startup disk.

Read more: Is Your Life Raft Ready

Is Your Backup Current?

You have probably noticed that Techtool Pro reminds you to back up your computer each time you launch it. (Unless of course, you've clicked the "Do not show this message again" checkbox.) In addition to being a good idea to back up in normal circumstances, it is an especially good idea if it could be a while before you have easy access to an Apple or Apple-authorized repair facility. While Techtool Pro's volume and partition repairs are great for logical problems, physical damage cannot be repaired in software.


When it comes to your backups, go with redundancy. If at all possible, try to have more than one backup available. Time Machine, built into macOS, is a great option. To add redundancy, consider the Techtool Pro cloning tool to make an exact copy of your startup disk to another drive or disk image that you can save in the cloud. It might even be a good idea to have an unused external solid state drive to use as a startup disk in a pinch.

Read more: Is your backup up to date?

Predicting Hard Drive Failure

Here at Micromat, as you might imagine, we're pretty good at destroying drives in our computer testing lab. The rigors of software development, as well as testing Volume Rebuilds and Optimizations often take a toll. Some of the machines in the office are on their third or even fourth internal hard drives. More often than not, a SMART warning gives us the early warning we need to keep our Macs running.


A while back, one of the Mac minis in our lab was starting to boot up more slowly than it used to. After checking the drive in the Mac mini using Drive Scope, we found that it was reporting a SMART warning. On further inspection, the drive was reporting over 100 uncorrectable ATA errors and a number of pending relocated sectors, indicating that the drive could soon begin reporting bad blocks. And sure enough, within a month the Surface Scan test in Techtool Pro was reporting bad blocks. We were able to replace the rotational hard drive in this older laptop with an SSD, so it starts up faster than ever.

Read more: Predicting Hard Drive Failure

Getting the most out of your Protogo devices


Techtool Pro's Protogo tool is useful for creating a dedicated diagnostic device that you can use to start up your Mac (and other Macs compatible with your OS) for troubleshooting and repair. To get the most out of your Protogo device, it is important that you choose the right drive.

The faster the drive you use for your Protogo device, the better your experience will be. For the absolute best results, use an external SSD connected via Thunderbolt or USB 3.1. If you are using a thumb drive, they vary very widely in terms of performance. In our experience, the very best performers (which can still be found for less than $20) are those which utilize a small SSD inside the thumb drive. Some such examples can be found here. At the minimum, it is best to use USB 3 or 3.1 USB sticks, even on USB 2 equipped Macs, because the memory they use is still faster when connected via USB 2. (And many USB 2 devices use memory that is much slower than the connection itself.)

Read more: Getting the most out of your Protogo device

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