DiskLoomDisk Utility can tell you whether a volume and file system are usable, but that is not the same as understanding the physical SSD. Modern drives keep their own telemetry: Apple NVMe metrics for internal storage and SMART data for many SATA, NVMe, and external devices.
The five signals that matter
1. Endurance used
Flash cells wear as data is written. A drive reporting one percent used has consumed roughly one percent of its rated endurance; it does not mean the drive has only one percent health. Watch the trend and your write rate.
2. Available spare
SSDs reserve spare flash to replace cells that can no longer be used reliably. Falling spare capacity, especially alongside errors, deserves attention.
3. Media and data-integrity errors
A rising error counter matters more than a static historical value. Back up first, then compare new samples to see whether the problem continues.
4. Temperature
Brief temperature peaks can be normal under load. Sustained heat or a new pattern is more useful than one isolated reading.
5. Power-on age and write rate
Age, workload, and reported wear together provide better replacement context than any single health score.
How to interpret the result
A healthy result means no current warning signs were detected in the telemetry macOS exposed. It is not a guarantee against sudden failure, accidental deletion, theft, or file-system damage. A recent backup remains essential.
Important: If macOS does not expose telemetry for a device, the honest result is unknown. Missing data must never be converted into a healthy status.
A repeatable check
- Confirm that the physical drive exposes usable telemetry.
- Review endurance, spare capacity, errors, and temperature.
- Compare the current sample with earlier samples.
- Check that your latest backup is available.
- Act on changes, not merely alarming-looking raw numbers.