Ok, so the TS3400 is reloaded with root disabled:
ran tests
root@debian:~# dd if=/dev/zero of=/dev/md10 bs=1G seek=22000 count=1
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 58.6727 s, 18.3 MB/s
root@debian:~# dd if=/dev/md10 of=/dev/null bs=4k count=10240
10240+0 records in
10240+0 records out
41943040 bytes (42 MB, 40 MiB) copied, 0.298845 s, 140 MB/s
root@debian:~#
and now having some problems problems formatting the array
root@debian:~# mkfs.ext4 /dev/md10
mke2fs 1.44.5 (15-Dec-2018)
/dev/md10 contains a xfs file system
Proceed anyway? (y,N) y
Creating filesystem with 5826563584 4k blocks and 364161024 inodes
Filesystem UUID: dfb8c4e4-3aba-4bfb-93e5-82c9a22e371d
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
102400000, 214990848, 512000000, 550731776, 644972544, 1934917632,
2560000000, 3855122432, 5804752896
Allocating group tables: done
Writing inode tables: done
Creating journal (262144 blocks): mkfs.ext4: Attempt to read block from filesystem resulted in short read
while trying to create journal
root@debian:~# mkdir /mnt/array
root@debian:~# mount /dev/md10 /mnt/array
mount: /mnt/array: wrong fs type, bad option, bad superblock on /dev/md10, missing codepage or helper program, or other error.
root@debian:~# uname -a
Linux debian 4.19.0-8-armmp-lpae #1 SMP Debian 4.19.98-1 (2020-01-26) armv7l GNU/Linux
root@debian:~# mdadm --detail --scan
ARRAY /dev/md0 metadata=0.90 UUID=520ff40a:771a4a9a:e97df895:e01ccbc7
ARRAY /dev/md/1 metadata=1.2 name=TS3400D-EMAEA:1 UUID=bc2a312c:9e69a15e:e2c23f68:356e26a7
ARRAY /dev/md/2 metadata=1.2 name=TS3400D-EMAEA:2 UUID=8fed1747:dedae5ac:02cdf5ff:0606eba5
ARRAY /dev/md/10 metadata=1.2 name=TS3400D-EMAEA:10 UUID=998beb61:15e2396c:306eea0a:54ff59c9
root@debian:~#