System volume root's usage is 96%. This condition should not occur under normal conditions

Hello All,

I realize this question has been asked many times, as I have read a bunch on the error: System volume root's usage is 96%. This condition should not occur under normal conditions.

I have an RN51600 with 24TB running firmware 6.8.1

I have no apps installed and only use "Sync with Amazon Cloud Drive" which currently syncs 9TB of data. 90% of which is photos.

I have had 4 ReadyNAS devices and at all have given me similar errors at some point in time, but never to thie level. They all semmed to continue working, but now that I am 96%, I cant even install the firmware to 6.9

Below is the info from the Volume log. 

I am not really familiar with SSH and use Mac computers. I am more than willing to turn on SSH if someone can talk me through clearing the volume and helping me stopp the problem with it filling up. 

THANK YOU!

=== df -h ===
Filesystem Size Used Avail Use% Mounted on
udev 10M 4.0K 10M 1% /dev
/dev/md0 4.0G 3.8G 31M 100% /
tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs 1.9G 54M 1.9G 3% /run
tmpfs 960M 1020K 959M 1% /run/lock
tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/md127 19T 8.8T 9.4T 49% /data
/dev/md127 19T 8.8T 9.4T 49% /home
/dev/md127 19T 8.8T 9.4T 49% /apps
tmpfs 50M 0 50M 0% /var/replicate/shm
/dev/md127 19T 8.8T 9.4T 49% /var/ftp/backup20150821