Comment 11 for bug 182931

The speed drops because at the beginning of writing the data will be copied to the filesystem cache and only after this file system will try to flash the cache to the usbdrive. If the drive is to slaw it will reduce copy speed. Normally if file system mount with option sync no cache will be used and you will see real speed of your drive.

Do you have any linux configurations where it hase better speed ? What say kernel log about this, are there any warnings ? Use dmesg to find this out.

Try fallowing test. Umount your usb stick, start terminal and run this commands:

sudo mount -o sync /dev/sdb1 /mnt/
# will mount with option sync usb stick if it located on /dev/sdb1 to the directory /mnt

sudo dd if=/dev/zero of=/mnt/test.dd bs=1M count=100
#will write 100M to usb drive and return writing speed.

My Kingstone usb-stick will return:
104857600 Bytes (105 MB) kopiert, 130,25 s, 805 kB/s
This is normal, real speed if sync used.
Write speed depends on filesystem block sice.