If files were corrupted out of the blue, an external drive you usually connect to the Mac doesn’t operate properly, or your computer doesn’t boot, then it’s time to check the health of your hard disk using Disk Utility via the S.M.A.R.T. status that a lot of disk drives include. This is a feature that lets a disk drive test itself for potential problems.
What is SMART Status?
S.M.A.R.T., also written as SMART, is the acronym for Self-Monitoring, Analysis and Reporting Technology. It is a hard drive and flash disk monitoring system that tracks indicators of drive reliability and informs the user about them, allowing enough time for data backup if needed. The disk health monitoring technology was standardized by the Small Form Factor (SFF) committee in the mid-90s, based on technology developed by computer manufacturer Compaq and disk drive makers Seagate, Quantum and Conner.
The most basic information S.M.A.R.T. provides is the S.M.A.R.T. status, which includes two values, “disk OK” or “disk drive fail”, which are based on the values “threshold not exceeded” and “threshold exceeded”. More information about the drive’s health can be obtained by examining the S.M.A.R.T. attributes, which monitor a variety of metrics such as read error rate, disk surface error rate, spin-up time, data throughput, write-head stability, and spin-up retries, among many other options.
Each attribute has an absolute value (raw) defined by the manufacturer and a normalized value on a scale of 100 to 1 or 200 to 1. When operational, the drive monitors how often these metrics hit a warning threshold. If that happens repeatedly or for prolonged periods of time, the user will receive a warning message that the S.M.A.R.T. monitoring has detected an error that needs to be addressed. When a Mac optimization app or Disk Utility notifies you about S.M.A.R.T. errors, it likely means the hard drive is going to fail sometime soon – which could be anywhere between hours or even weeks. Unsuccessful attempts to repair the startup disk using Disk Utility will ultimately lead to a new HDD or SSD purchase.
How to Check S.M.A.R.T. Status on Your Mac?
The S.M.A.R.T. status of the built-in hard drive, SSD or external disk volumes can be checked by launching Disk Utility and clicking on the disk listed in the left pane of the window. The status displayed by Disk Utility will be one of the following:
- Verified: Your disk has been checked and is likely healthy.
- Not supported: A message displayed on 2015 and newer MacBooks, and late-2016 and newer MacBook Pros.
- About to fail: The drive you are checking has failed some of the regular tests, which indicates a likely failure. If you are going continue to use the disk as your startup drive, the best thing to do is to back up the data and replace the drive with a new one immediately. If this isn’t your startup drive, you may accept the changes and do some troubleshooting. For example, try to repair the drive with Disk Utility or erase and format the disk. If the problem was minor, the hard drive will likely be restored to its former health.
S.M.A.R.T. Not Supported
While the “S.M.A.R.T. Not Supported” status appears regularly when checking external hard drives, owners of the MacBook Pro (late 2016) will also get this message when checking the status of the built-in SSD. The reason is because Apple dropped support for S.M.A.R.T. status starting with the 2015 MacBook as it switched to PCIe solid state drives.
PCIe SSDs don’t support S.M.A.R.T. because Apple considers this subsystem obsolete. In a support document initiated by an early 2017 MacBook Pro owner asking the community for answers regarding the lack of support for S.M.A.R.T., the Apple-recommended answer to the question was that S.M.A.R.T. status is for rotating mechanical drives.
That doesn’t prevent SSD manufacturers such as Intel or Samsung supporting S.M.A.R.T. on their products, however, so if you replace the old HDD with an SSD then in all likelihood it will be possible to check the S.M.A.R.T. status of the startup disk. It remains to be seen, though, what methods Apple will use to check the health of a PCIe SSD and how it intends to inform the user if the drive is about to fail.
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