The perfect time to know about the health of your hard drive is not when it finally crashes: that is the point at which it has stopped recording information about itself. There are a few free built-in utilities that will give you the same data from the drive in just a few minutes. In this section, we’ll show you how to get an idea of your hard drive’s health on both Windows and Mac computers, what parts of that data to pay attention to, and how to determine whether or not you need to start backing up your data and replace the failing device.
Every modern drive checks itself using something called SMART. Free and built-in utility software reads the SMART data stored on your drive and provides various pieces of information such as the number of reallocated sectors, pending errors, and an overall “pass” or “fail” status. As soon as you see any type of warning message from SMART, you know your drive is starting to fail and it is time to back up all data as quickly as possible.
Hard drives (as well as solid state drives) use something called SMART (Self-Monitoring, Analysis and Reporting Technology): a method that allows them to continuously monitor their own operation and report on numerous attributes they track themselves. These attributes include dozens of different types of data that are logged internally by the drive. But for all practical purposes, you only really need to focus on a handful of those categories: reallocated sector count (the total number of bad spots that the drive has identified and automatically swapped out for spare areas), pending sector count (spots that the drive suspects and is waiting to deal with), and an overall pass/fail status. A new hard drive would typically display zeros for all of these items, while an old drive in good condition would likely display very small values for these metrics. Anytime either of these values is high or continues growing every time you access these parameters, it indicates your hard drive is gradually getting worse and that is literally the best piece of information provided by a health check.
Beginning with Windows-based systems, one of the best tools to quickly read what is going wrong with a drive is a free tool called CrystalDiskInfo. The tool displays the health status of every single drive in terms of “Good”, “Caution” or “Bad”. Additionally, it provides an easily understandable list of the SMART attributes of the drives, allowing you to see the reallocated and pending sector counts as well. A quick built-in check in Windows is to start the Command Prompt and run wmic diskdrive get status, which will show “OK” or a warning message for each drive. The tool that scans the file system and surface for errors is chkdsk (or right-click the drive → Properties → Tools → Check), which flags and marks bad sectors. However, when checking the file system for errors on a drive you believe is failing, make sure to back up your data first, because running a full check works the drive very hard.
For Mac-based systems, the native application for beginning this process is Disk Utility → First Aid. This tool runs through and checks and possibly fixes the structural elements of the file system of the selected drive. In order to access the SMART status, click the Apple menu, then select “About This Mac,” then select “System Report.” Selecting “Storage” under “Hardware,” there should be SMART status displayed for each of your drives. Either they should display as “Verified” or “Failing.” For the detailed SMART attribute information (such as the number of reallocated and pending sectors), use the free command-line tool smartctl (part of smartmontools). Like Windows users, you may use First Aid without concern. However, similar to Windows users, if your drive is producing noise or is otherwise struggling, get your data off the drive prior to using any kind of repair.
Interpreting a check is much easier than it seems. An overall status of Good, OK or Verified with zero or low, unchanging reallocated and pending sector counts means the drive is healthy: simply check again in a few months. Any reallocated or pending sectors that are present and, worse, growing between checks mean the drive is slowly failing, so back up now and plan to replace it. A status of Caution, Bad or Failing means act today. And keep the limits in mind: SMART sometimes passes a drive that later fails, so if your drive is clicking, running slowly or losing files, trust the symptoms over a clean result. If a drive has already failed, a hard-drive recovery is from £300 +VAT.
The quickest way is a free tool such as CrystalDiskInfo, which displays a Good, Caution or Bad status along with the SMART attributes that matter most, mainly the reallocated and pending sector counts. For a built-in check, open Command Prompt and enter wmic diskdrive get status, and use chkdsk to scan for file-system and surface errors, though only after backing up if you already suspect the drive.
On a Mac, start with Disk Utility and run First Aid to check and repair the file system. For the drive’s SMART status, go to the Apple menu, About This Mac, System Report, then Storage, and look for Verified or Failing next to your drive. To view detailed SMART attributes such as reallocated sectors, you can use the free smartctl command-line tool on macOS.
A “good” drive will have an overall health rating of “Good”, “OK” or “Verified,” and near-zero numbers (and constant) for both reallocated and pending sectors. Brand new drives show nothing but zeros. It’s the trend line that matters, though. The trend lines of increasing sectors every time you run a SMART test indicate that the drive is degrading, and may be headed toward failure, even when the overall health rating remains “OK”.
Yes. Even though SMART provides some degree of insight into how well a drive is performing, there can be times when a disk fails without displaying anything wrong in its SMART testing, especially from sudden mechanical or electronic faults. As such, while a good SMART report should provide some level of comfort, it doesn’t mean you shouldn’t back up your data as soon as possible. For example, if your drive starts to make noise, slow down significantly or lose files, you should treat these symptoms as serious indicators of potential disaster and immediately back up your data.
Yes, this is correct for a healthy drive. CHKDSK is simply a maintenance program. But, if the drive has been acting poorly, i.e. making odd noises, running much slower, or suddenly showing loss of files etc., then it would be wise to perform a backup before attempting to use CHKDSK. This is because performing a full CHKDSK run puts additional stress on the drive. And, depending upon the type of problem with the drive, using CHKDSK could potentially write over recoverable data. Or, in the case of a physical fault, make matters worse. If the drive is noisy or clearly struggling, it is better to send the drive in for diagnosis rather than scanning it.
If a check shows a growing number of bad sectors or a Caution status, or the drive is already behaving erratically, do not wait for it to fail. Send it in and we’ll tell you what’s recoverable, with a free diagnostic and a fixed quote first.