smartctl often shows fewer or limited SMART parameters for USB-connected drives (external HDDs/SSDs in enclosures or via adapters) compared to internal SATA/NVMe drives. This happens mainly because USB drives use a bridge chip (USB-to-SATA or USB-to-NVMe) that translates commands between USB (typically SCSI-based) and the internal drive's ATA/NVMe protocol.
Key Reasons for Limited Parameters
USB Mass Storage protocol lacks a standard way to pass through full ATA SMART commands. The bridge may support only basic queries, proprietary methods, or none at all, resulting in incomplete attributes (e.g., only temperature, reallocated sectors, or a subset visible).
Many bridges filter or block advanced SMART features for cost, compatibility, or design reasons. Some external drives (especially WD/Seagate portables) intentionally limit passthrough.
Even with support, bridges often expose fewer vendor-specific attributes than direct connections.
Workarounds to Get More Data
Try specifying the device type with -d:
-d sat — for bridges supporting SAT (SCSI/ATA Translation) passthrough, common in modern UASP enclosures.
Other options: -d sat,12, -d usbjmicron, -d usbcypress, etc. (check smartctl --scan or the supported USB devices list).
Example: sudo smartctl -x -d sat /dev/sdX ( -x shows extended info, more than -a or -A).
Update smartmontools and its drive database: sudo update-smart-drivedb.
For some bridges (e.g., certain Seagate/WD), disable UAS mode via kernel quirks to fall back to usb-storage, which may enable better passthrough.
Best full access: Connect the drive internally via SATA (shuck the enclosure if possible).
In summary, this limitation stems from USB bridge hardware/firmware constraints, not smartctl itself. Many users report only partial attributes over USB, even when the drive supports full SMART internally. For critical monitoring, prefer direct SATA connections.
lsblk
lsusb
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