## TL;DR
A USB drive dropping mid-job is usually power, cable, hub, or the drive itself sleeping or failing. Check system logs for the disconnect time, move the drive to a direct port with a short known-good cable, disable USB selective suspend for the backup window, test the drive health, and rerun; treat repeats as a dying drive until proven otherwise.

```text
backup failed: USB drive disconnected mid-job
```

## Use this when
- Backup software reports target errors at the moment the OS logs a USB disconnect.
- The drive reappears seconds or minutes later with a new mount.
- Jobs to internal or network targets on the same machine succeed.

## Not for this skill when
- The target is a NAS dropping over the network. Different transport.
- The USB drive never appears at all. Enumeration problem, not mid-job drops.

## Steps
1. Correlate backup failure times with OS device disconnect events. Verify: disconnects and failures align in time
2. Reconnect the drive on a direct motherboard port with a different short cable, removing hubs. Verify: the drive enumerates stably
3. Disable USB selective suspend and drive sleep in power settings for the backup period. Verify: power settings are changed and saved
4. Check drive health with SMART and a full surface read test. Verify: drive health is reported good or faults are found
5. Run the backup again while watching device events. Verify: the job completes with no disconnect events

## Variant phrasings
### usb external drive disconnects during backup
The symptom phrasing.
### backup target usb dropped mid job fix
The job variant.
### usb drive disappears backup power cable
The cause wording.

Compatibility: USB 3 external hard disks and SSDs on Windows 11 and Linux desktops and small servers used as backup targets.

## Why it happens
Bus-powered drives at the end of long cables or unpowered hubs brown-out under sustained write load, exactly what a backup produces, and power management can suspend a device the OS thinks is idle between bursts. The drive electronics or a failing disk add the third cause. All three present identically in backup logs, so log correlation and substitution are the diagnosis.

## Edge cases / pitfalls
- A powered hub or a Y-cable fixes genuine power starvation but masks a failing drive. Still run health checks.
- Rotating two USB drives spreads risk, but both need health checks, not just the failing one.
- If disconnects follow the drive across machines and cables, retire the drive. It has told you enough.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_eMbOe0Dyr-zJLP47R4mp7w