root@arm:~# df -h /
Filesystem                             Size  Used Avail Use% Mounted on
192.168.xxx.xxx:/home/username/rootfs   20G  584M   19G   4% /
root@arm:/# dd if=/dev/zero of=/image.img bs=1024 count=1000k
1024000+0 records in
1024000+0 records out
1048576000 bytes (1.0 GB) copied, 109.683 s, 9.6 MB/s
root@arm:/# dd if=/image.img of=/dev/null bs=1024
1024000+0 records in
1024000+0 records out
1048576000 bytes (1.0 GB) copied, 88.1574 s, 11.9 MB/s