USB Transfer Speed 5MB/sec & dropping

Hi all
I’m trying to copy the contents of my home folder to USB 3.0 and the transfer speeds are hopeless!! It’s starts around 100MB/sec and at around 1GB it drops to 5MB/sec??? Total size of the home folder is 274.4 GB and the estimated time 38+ hours!!!

Help, Please :-s

Then your dirty cache on the RAM must be about 1G. The speed of 100MB/s is first the transfer speed to RAM and when it is filled you see the actual speed. It writes in the background. The RAM cache acts as buffer. So 5MB/s cannot be an USB3 Device, even if you plug in an USB2 device in an USB3 port, it doesn’t become an USB3 device.

The only problem I see here is that the buffer is way to high for your usb device.


Probably this:


For example to test it:

  1. Get the block device name of the usb device:
lsblk -fs
  1. Replace <replace_me> with sda, sdb or sdc etc. what ever lsblk shows you. That limits this device to 16MB buffer instead of 1GB.
sudo bash -c 'echo 16777216 > /sys/block/<replace_me>/bdi/max_bytes'
sudo bash -c 'echo 1 > /sys/block/<replace_me>/bdi/strict_limit'
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long time ago but there is a solution to copy this large size via usb.

It has been discussed a lot of times and there is several ways to achieve the goal of being able to safely remove the USB stick when copying has been done.

It is a fact that Linux kernel is very good at what it is doing - using the hardware efficiently - but the human point of view sometimes differs.

That is how it is.

1 Like

Some options you could try:

  • Use a different USB port.
    Sometimes the ports have different chips. Then it may be that a USB device runs better on one port than on others.
  • Use a different USB stick
    Some USB sticks are big, but not really fast. Even if it says USB3, it’s not necessarily a fast stick.
  • Use an external hard drive instead
    Anything over 16GB data volume is actually not an issue for a USB stick, but either for an external hard disk or for an external SSD.
  • Compress the data before copying (zstd)
    Compression rates of 2:1 are often possible without any problems, which easily halves the time required for copying.

How big is your usb-stick ?
500GB ?
Are you sure it is not a fake ?