Still your writing speeds are low, I just connected a usb-2.0-sata interface to the white usb with settings mount as external share. The disk in this interface is an old maxtor 250 GB disk formatted in ext3 using samba 4
For big files
writing speed (to the rspb4) was 30 MB/s
reading, windows says 112 MB/s but on usb-2.0 max speed is 480 Mbits/s so thats a little strange
For small files
For 1 GB of small files the writing speed is most of the time 22 MB/s sometimes for short period dropping to 12 MB/s
Reading speed 45 MB/s sometimes droping for short time to 15 MB/s
So much better then your performance this could also be related to the performance of your PC's hard disk
The function which failed was "initialising" disk from the disk setup-setup menu. I saw that the disk setup- external disks menu has a format function when a disk is identified as external. I would consider usb connected disks as external but they do not show up here. So I am wrong somehow!?
Yes something is not right there I tried to format the trial disk using the initialize function, it succeeded to remove partition table but failed to format the disk with message could not the disk, like you had .
Also it is identified as sda while it should be sea when it is classified as external disk, so we will investigate there what is going on
Next test is testing speed with disk mounted as internal disk