You have a very slow hard drive
There are four things that matter for transfer speed between storage devices.
- How fast the source reads
- How fast the target writes
- How fast the bits can be moved between them
- What post-write nonsense is done.
USB sticks tend to be flash memory with relatively equal read and write speeds, but the spinning disks in a hard disk drive are noticeably unequal. So, unless the USB is very slow, you’d expect a USB to HDD copy to be slower than either USB to USB or HDD to USB.
You can also be slowed down by antivirus scans, on-disk encryption, search indexing, or even the need to move bits from the USB bus to the HDD controller.
Spinning media is slower than solid state NAND storage
Sata is 6gb/s at its fastest which is what most hdds connect with. Your nvme depending on pcie version and then even your usb port speed all matter. I have a pcie5 nvme my mobo supports the usb c type gen 69420 street fighter alpha 3 which tops out at 40gb/s I think. I also bought the fastest Kingston traveller usb stick I could. It’s pretty fast. What I’ve found is the diff between pcie5 and 4 is really not noticeable to me. Nice to have but I think I should have bought a bigger pcie 4 than a 1tb 5 nvme.
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Hard drives are slow. These are mechanical devices that have to physically move the header to the right place. Add data fragmentation that multiplies the movements on top of that and it’s a performance nightmare
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Kinda depends on all 3 devices. Some USB devices can have extremely high burst rates before they’re heat saturated or some have ssd’s built in that can nearly peg the bus speed. Slow spindisks would be in the range of 80 mb/s or so where fast ones like sata Exos drives would be nearly 300 mb/s and sas even faster, some even bursting to max out the bus speed with their cache. Another factor is the load itself. Random access data is incredibly slow on spindisks compared to virtually any USB device, meaning lots of small files are going to crawl compared to big ones. Bit locker and tpm could be slowing it down if it needs to decrypt which isn’t likely slowing the USB drives down.
I think you’d get a better set of potential issues by being specific about the devices and interfaces.
