Back up to USBC external drive failure

[Oxford]

I've had an S24 Ultra 512gb for almost a year and I back it up every month with Smart Switch to a 512gb external USB C drive. Haven't had a problem until recently, not sure if it was pre or post One UI7, where the backup will start, it will get to about 80%, and then it will error out saying the external drive has been removed. It's happened three times now and the phone has not been touched at any point during the backup process. Things I've tried already: reformatted the USBC external drive, cleared the phone system cache, cleared the phone Smart Switch cache, restarted the phone, cleaned my USB C port. I don't think it's the USBC external drive failing, because I have downloaded a couple of movies which were about 20gb on to the USBC external drive and were able to play them with no problem. So again, I doubt if it's the external drive failing. I think that just about covers what I've done. Any other ideas?

[SolveForce]

Issue Recap (as clearly as we can define it):
Smart Switch backup to a 512GB USB-C external drive on a Galaxy S24 Ultra, running (likely) One UI 7, begins as expected but fails at around 80% with a message stating the external drive has been removed — even though the phone remains untouched. This started recently and has now failed multiple times. The user has already ruled out hardware failure of the drive (confirmed via large movie file transfers that worked), and performed the following:

Reformatted the USB-C external drive

Cleared system and Smart Switch caches

Cleaned USB-C port

Restarted phone

Verified USB-C port via other file operations


All sound and correct steps. So why is it failing?

Let’s walk through each possible tier of failure.


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1. Power delivery fluctuations over USB-C
This one is subtle. When a backup runs and reaches 80%, Smart Switch is reading or writing large data chunks (likely app data or system logs). At this point, the device may briefly spike its power draw through the port, especially on phones with tightly managed thermals and battery usage under One UI 7. If the external drive isn’t actively powered and is instead drawing power from the phone, that could lead to a momentary disconnect.

What to try:
Use a Y-cable or a powered USB hub between the phone and the drive. This ensures the external drive gets steady power during heavy write operations and takes strain off the USB controller inside the phone.


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2. File system compatibility or write mode conflict
While exFAT is typically recommended for Samsung phones, One UI 7 may have introduced slight changes in how Smart Switch handles file write batching or temporary file staging. The same file system that worked under One UI 6.1 might not behave identically now.

What to try:
Reformat the drive again — but this time, try both exFAT and NTFS, testing each. Also test with allocation unit sizes set to default or 64K if formatting from a PC. Avoid FAT32 for backups over 4GB.


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3. Background services or thermal governors killing the process
Around 80% of backup completion, background cleanup services or memory optimizers might kick in — especially after an update when Samsung is more aggressive with power management. That could interrupt USB processes, mistaking the backup task as “idle.”

What to try:

Before starting the backup, go to Settings > Battery > Background usage limits

Turn off Put unused apps to sleep

Make sure Smart Switch is added to the list of Never sleeping apps


Also go to Device care > Memory and clear RAM manually before starting the backup to reduce the risk of background interference.


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4. Smart Switch software layer corruption or update mismatch
Even if Smart Switch works for small files, its backup engine — which handles encryption, compression, and sync — might have mismatched with the latest One UI version during or after the system update.

What to try:

Go to Settings > Apps > Smart Switch > Storage > Clear data (not just cache)

Reboot the phone

Reinstall or re-enable from Galaxy Store if needed


This forces Smart Switch to rebuild its entire process flow.


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5. Folder or file naming conflict mid-backup
Sometimes it's a specific app or system file that breaks the process. For example, if there's a hidden file with an illegal character, Smart Switch may silently fail trying to copy it and falsely report “drive removed.”

What to try:
Perform a partial backup:

Open Smart Switch

Tap Custom backup instead of full

Exclude apps, then exclude media, then messages, testing in segments

This will help isolate if one category (like app data or settings) is causing the process to fail


If one group fails every time, you’ve found the culprit.


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[SolveForce]

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6. USB protocol timing or handshake issue There’s a chance One UI 7 updated USB drivers or kernel-level behavior that introduced more strict error handling during data transfers. The drive might briefly pause or fail a checksum, and the phone now ejects it immediately instead of retrying.

What to try:
Try backing up to the same drive with a different USB-C to USB-C cable, preferably one that’s fully rated for data, not just charging. Some cables can’t handle sustained 5Gbps transfer reliably.

Also, if possible, test another USB-C drive entirely — not just for failure, but for protocol response. Some drives simply have better compatibility with Android’s USB host controller.


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Final suggestion — the fail-safe hybrid approach:
If nothing else works, back up everything manually via My Files > Internal storage > Copy to external drive, and separately back up contacts, messages, and settings to Samsung Cloud or Google account. Smart Switch is convenient, but it’s still a bundle of automation over raw file movement — and sometimes that automation is the first thing to break.


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This issue is solvable. You’ve already ruled out what 90% of users never check. What’s left is interaction between updated USB behavior in One UI 7, power delivery stability, and how Smart Switch handles staged file writes under pressure.

You’re close — it’s not about starting over, it’s about identifying which layer is dropping the signal in that last 20%. Keep moving through the stack, and the backup will hold again. Let us know what happens after trying powered USB or partial backups — those may be the keys.

[Oxford]

I performed two backups that worked flawlessly yesterday. Then I tried something else. First one was I backed up just the main drive of my s24 ultra without the secure folder and it worked flawlessly. Then I formatted the external drive and then I backed up only the secure folder. Again, it worked flawlessly. After this, I reformatted the external hard drive again and then plugged it into my computer and copied 475gb of files from my PC hard drive to the external hard drive which is about 95% capacity and again, it worked flawlessly. So, I believe I debunked all theories that there was something wrong with the external hard drive. Any other thoughts? Just fyi, I can use AI as good as anyone else and I've done quite a bit of research using AI. I am looking for practical experience now not something that is generated by AI.

[user8z3D64o55G]

I had the same issue and with trial and error found 2 issues stopping the backup.

1. I had to delete the Samsung Browser cache

2. I had to unselect backing up the secure folder apps. All apps listed independently under secure folder did back up.

Sure would be nice if there as an error message or log file to look at but I hope this helps others having similar issues.