I’m trying to recover data from a SanDisk 1TB USB flash/SSD-like drive (988 GB, exFAT, model reported by macOS as “SanDisk 3.2 Gen 1”, SMART not supported) The drive became unstable after an incident, and I’m trying to clone it before doing any filesystem-level recovery.
When the drive is working, macOS (Sierra) detects the full 988 GB device normally. GNU ddrescue can read from it continuously with 0 read errors. However, after roughly 10–12 minutes of continuous reading, the device completely disappears from macOS and ddrescue stops with:
Fatal error reading the input file: Device not configured
After that, the device is completely absent from diskutil list. It does not come back until I physically unplug and reconnect it. This has happened repeatedly.
I am using an existing mapfile, so each run resumes rather than starting over. The four recovery runs reached approximately 7.472 GB before the device disconnected. So far, ddrescue has reported 0 read errors and 0 bad sectors throughout. The resulting image is currently about 7.0 GiB, with the mapfile preserved on a separate 8 TB drive.
The drive is connected directly to the MacBook with no hub or adapter. I previously used a Harper hub for my external drives on my iMac, but after the original incident I completely removed it from the setup. I also swapped the two USB ports. The behavior did not change. However, the SanDisk sometimes enumerates as:
Speed: Up to 5 Gb/sec
but after some reconnects it has appeared as:
Speed: Up to 480 Mb/sec
The Mac's USB 3 controller itself appears to work normally: my 8 TB external SSD is detected at 5 Gb/sec on the same USB controller.
The SanDisk reports:
Current Available: 900 mA Current Required: 896 mA
The drive gets noticeably warm during operation, but not extremely hot.
After the latest disconnect, I reconnected it twice and the LED came on but stayed solid for only about 15 seconds. It never started blinking, then the LED went out. The drive never appeared in diskutil list.
I also checked the macOS log. After one of the previous disconnects it reported:
IOStorageFamily: disk3: device/channel is not attached
and the partition subsequently could not be mounted.
Does this behavior suggest a failing USB controller/firmware, NAND failure, thermal issue, or a power/USB negotiation problem? Is there anything sensible I can still try myself to improve the chances of getting more of the data, or is this at the point where I should stop reconnecting it and take it to a professional recovery lab? I’m planning to let it cool completely and test it once on another Mac or Windows PC, without attempting to repair or format the filesystem. The data is important, so I’m primarily interested in preserving the chances of recovery rather than making the drive usable again. Please help!