May i ask what the reserved space is good for?
from man mkfs.ext4:
-m reserved-blocks-percentage
Specify the percentage of the filesystem blocks reserved for the super-user. This avoids fragmentation, and allows root-owned daemons, such
as syslogd(8), to continue to function correctly after non-privileged processes are prevented from writing to the filesystem. The default
percentage is 5%.
I wonder why/where the initial 36 GB reserved space came from ?
How do you copy the 4TB back to the HD ?
from what OS ?
over samba share ?
I guess you meant Mbyte/sec ?
AFAIK a RasPi has a 1 Gbit LAN, so network speed should be 100-112 MByte/s
my WesternDigital WD-Black-P10 5TB could write 142 MB/s via USB connection
therefore you should see higher speed !
otherwise I guess with your disk is something fundamental wrong ?
and if so I would start over and delete all partitions from he disk.
I found a user friendly write up:
be aware: unmount the disk before !
on your PI (with NO external disk attached !):
- connect the external disk
- key in "mount" to find out what's the disk device name is; usually /dev/sdbX
assuming /flash is mounted on /dev/sda1 and /storage is mounted on /dev/sda2, then the next free device name is /dev/sdb (your external disk, usually mounted under /var/media (?!)
(I got no PI here, so please correct me if I'm wrong !)
- unmount it:
either "unmount /var/media" or "unmount /dev/sdb1", but remember the device name, e.g. /dev/sdb
- recheck if it's unmounted with an subseq. "mount"
- after that read under the above linked page:
- how to print the current disk layout
- how to delete a partition
- how to create a new partition table
- how to create a new primary partition
- how to format that new partition with ext4
be aware:
to work on the correct disk (the above mentioned "device name" (/dev/sdb)
[ where "sdb" is the whole disk and "sdb1" is the first partition on that disk]
1. start parted with the correct unmounted device name:
parted /dev/sdb (it starts a sort of subshell indicated by a prefix "(parted)" and operates on the device /dev/sdb"
2. key in "print" to make sure you're on the correct disk
if so
3. rm <the partition number goes here> [see chap. 6 in the linked page]
and if the disk contains more then one partition: repeat until the disk has no partition anymore !
4. now we create a new partition table GPT and a primary partition [see chap. 4 in the linked page]
- adjust "mklabel msdos" to "mklabel gpt" !
- key in "mkpart"
- key in "primary" !
- ext2 is okay (we change it later; btw.: ext4 is an ~enhanced~ ext2)
- Start? is 1 (if parted suggests 2: the disk still contains partitions => goto 3.)
- End? is what parted suggests justed confirmed with enter key
- key in "print"
now the disk should have:
- Partition table: gpt
- one partition => Number is 1 !
- size is 5 TB
- type: primary
- FS: ext2
- flag: don't know
is so ???
5. key in "quit"
you're now out of the parted subshell; the command prompt starts with "LibreELEC:"
6. I'm unsure if parted informs the kernel over the new partition, but it want hurt to key in "partprobe"
7. format the shiny new partition with
mkfs.ext4 /dev/sdb1
or with an disk label:
mkfs.ext4 -L <my-external-disk-label> /dev/sdb1
8. reboot the box and check
- new disk is mounted under /var/media
- has the complete disk size (5TB minus 5%)
- has sufficing speed:
a) change to /var/media (cd /var/media)
b) run for write speed:
dd if=/dev/zero of=tempfile bs=1MB count=10240
c) run for read speed:
dd if=tempfile of=/dev/zero bs=1MB count=10240
d) cleanup
rm tempfile
comments/rotten fruits ? 
backup doc's (parted):
it's not on my site here
, also - IIRC - when I was using LE release.
your english is readable !
: kodi crashed and restarted (not a reboot)