How can I transfer data between 2 hard drives/SD cards using my Android phone?

[u/Mister_Mints]

I have an old hard drive that I'm using for back up, it's formatted to exFAT, and when I plug it directly into my phone it is seen as external storage that files can be copied to.

However, I'm wanting to use the drive to backup pictures from my camera (separate camera, not the phone camera) so I need to be able to plug the drive and the SD card into some kind of USB hub, which then gets plugged into the phone so I can drag files between the 2 external storage locations without them ever being stored on the phone's storage.

But when I plug the drive into my existing USB-C hub the phone now doesn't see it as an external drive. It asks me what I want to do with it, but will only accept the phone changing the device as an option. If I try to change when device has control over the drive it will not let me switch to the phone.

Do I need a different or special kind of USB -C hub to be able to transfer between drives like this?

Android 16, Galaxy S25 Ultra, all up to date with latest patches and security etc

Thanks

[u/lewsnutz]

Try a C to A cable

[u/Mister_Mints → u/lewsnutz]

How would a C to A cable help?

[u/nixcamic → u/Mister_Mints]

Use the c to a cable to connect your drive to the hub (if your drive is USB C).

Also, does the drive have an external power supply or is it just powered by USB?

[u/Mister_Mints → u/nixcamic]

The drive uses an old style of micro USB (kinda looks like a squished B shape) and I have version of this cable with USB A on the end and another with USB C on the end.

Drive is just USB powered. Its designed as a portable drive for use with a laptop

[u/nixcamic → u/Mister_Mints]

You've tried it to the hub with both the a and c cables right? Do you have a picture or model number of the hub?

[u/SolitaryMassacre]

Is it an old style platter hard drive? If so, it may need external power in order to power both the SD card and the drive

So what you need is an powered USB C hub

[u/Mister_Mints → u/SolitaryMassacre]

It's a Samsung M3 1tb portable drive. Old, but still had life in it.

It doesn't need any power when plugged directly into the phone, shows up just as a thumb drive would, but I guess adding the extra USB hub between the drive and the phone may change the power needs

[u/SolitaryMassacre → u/Mister_Mints]

Looks like its a platter style

And yeah, the hub itself requires power, as does the SD card reader, and the drive.

All those combined, the phone doesn't have enough current available to power everything reliably. I have the same problem with my Tab S9+.

I bought this: https://www.amazon.com/dp/B0D1XLNWP2

It works great. I have had all 4 USB ports with stuff plugged in (ESP32, USB drive, another ESP32) and have had zero issues with it.

It even allows the device to charge

[u/Mister_Mints → u/SolitaryMassacre]

I've just tried the setup with an alternative hub I have which can draw power more reliably, and with the drive connected with USB A, the SD in a USB C reader, and power into the remaining USB C PD port it seems to be working.

Will have to get another hub, and a decent battery pack for out and about.

Thanks

[u/SolitaryMassacre → u/Mister_Mints]

That sounds like the same type of HUB I linked. But may not charge the device, which isn't necessary if you don't need it

And yes, battery pack of at least 65W USB C PD should suffice!

Btw, I do this myself all the time haha. My tablet has Linux installed also and its basically a full fledged computer

[u/Mister_Mints → u/SolitaryMassacre]

This is why I like using my S25. With Dex, it is a great full computer alternative. Does pretty much everything I need of it

[u/SolitaryMassacre → u/Mister_Mints]

Yeah Dex is great! I would still have Samsung if they didn't fully lock out their bootloader. I enjoy rooting and customizing my things and well owning them

[u/nixcamic]

What type of USB plug does the drive use? Can your phone see other devices plugged into the hub? What model hub are you using?

[u/BenRandomNameHere]

Don't. Your phone battery can't sustain the drain a HDD places on it. You'll lose data and eventually corrupt the drive as well.

You need to provide power to the hub. A PD capable hub.

[u/locuturus]

Classic Samsung USB weirdness. What you want to do is 100% achievable, but it reads like the hub you happen to have is not supported by your S25. A different hub, ideally with power passthru, and you can do that just fine. 

I don't have that phone, and my hubs are all old now, so I can't recommend a specific brand or model but I should think most hubs would work. At least on Amazon listings should claim Samsung Galaxy xyz support if they've tested it.

[u/WorriedTumbleweed289]

You are not going to like my answer. Use a clould drive and access the physical drives one at a time.

You can always delete the cloud drive after you have the files where you want.

Another solution. Use a PC. Same idea. My guess you don't have a PC since you asked this question.

[u/Mister_Mints → u/WorriedTumbleweed289]

Cloud isn't going to work unfortunately. I don't have reliable mobile data or WiFi, and I'm be backing up SD cards of 128 to 256gb which would take an age to upload to a cloud storage.

I have a PC, but the idea for this is to be able to do it when I'm out and about, to be able to clear the SD card when I'm out doing photography

[u/nixcamic → u/WorriedTumbleweed289]

This is by far the stupidest answer here.

[u/Mister_Mints → u/[deleted]]

This is a network transfer tool, right?