Storage media of all kinds, SSDs included, is consumable. That mean, eventually, it fails. That’s one reason backups are so important. To keep ahead of the game, macOS offers tools that can check the disk health of your SSD and other attached disks.
What Is Disk Health?
Spinning HDD drives have a failure curve sometimes described as a “bathtub.” When you first get an HDD, there’s a high chance of failure thanks to DOA units. If the drive spins up properly, then it will likely last for years before suffering a failure based on wear. There’s a high chance of failure at the beginning and end of the service life (the walls of the bathtub), but a relatively low rate of failure in the middle (the base of the bathtub).
SSDs, on the other hand, show a different failure curve. They still have the same high rates of early failure; like all electronic devices there’s a risk of mis-assembly and component failure.
But uniquely, the flash memory uses in SSDs can only survive a certain number of write cycles. When they fail, they fail completely: no data recovery is possible. So it pays to keep an eye on the health of a drive that might suddenly and irreversibly fail without warning.
Both failure types can be predicted and planned for in advance based on certain characteristic failure patterns. S.M.A.R.T (Self-Monitoring, Analysis and Reporting Technology) is an automated self-test system for SSDs and more traditional spinning HDDs. macOS keeps track of all your drive’s SMART status by default, and there are several tools that read this status with varying levels of detail.
SMART Status in System Report
1. Click the Apple icon in the upper left.
2. Hold down the Option key.
3. Click “System Information.”
4. Click “Storage” in the list on the left of sections.
5. Select the drive you want to examine in the list across the top of the screen.
6. The SMART status appears at the bottom of the info pane.
“Verified” means the drive has no reported problems. “Failing” means the drive has an error that will soon become “Fatal,” which means the drive has failed. SMART’s numerical error code system provides more information about the drive’s specific calamity, but the broad headline delivered by macOS is enough for guessing how soon a drive will fail.
Get Detailed SMART Status with smartmontools
If you have Homebrew installed, you can install
smartmontools to check your drives’ SMART status through Terminal.
1. Open Terminal and run the following command to install smartmontools with Homebrew:
diskutil list to find the drive identifier for the volume you want to test. You can also find the drive identifier in the system report from the last step under the title “BSD Name.”
3. Run the following command in Terminal to get the SMART status for the specified drive:
This will produce a detailed SMART report in standard output. If you want to save the SMART report to disk, you can send it to a text file with the > control character.
The produced disk health report will provide a highly detailed look at the drive’s health. The most relevant data is the verdict, which appears halfway down the report. At the bottom the vendor-specific SMART status can provide a glimpse into the drive’s deeper condition.
DriveDx is a drive diagnostic tool that provides the most detailed picture of your SSD’s health. This paid application can simultaneously scan all your connected drives, providing a complete picture of your storage system’s health. While the app is open, it continually monitors SMART status for indication of failure or problems. It’s the easiest way to a detailed picture of your disk’s health without sifting through technical logs.
It’s a good idea to keep a casual eye on the health of your SSDs, but you don’t need to become obsessive about it. System Report will provide sufficient monitoring capability for the average user. More enthusiastic users can apply smartmontools through the command line. The most sophisticated users with will appreciate the quality-of-life upgrades and expansive detail of DriveDx.
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