Does anyone have a clue what is going on with this? I have a 16GB Nexus 4 rooted running CM 10.1 with TWRP installed as my recovery. I installed DiskUsage and my "system data" shows 8GBs of space being taken up leaving me with only 1.2GB free on my device. I read in a N7 post elsewhere that he rebooted and it magically reappeared but this is not the case for me. Other ideas?
you could download ES File Explorer or any file explorer, and see the properties(the size) of every single main folder stored on your 'virtual' SD card...the space may easily been used by downloaded ROM's ,nandroid backups ,videos ,photos...you could check the apps installed(Settings,Apps)...pardon me for the analogy, i have a strange imagination and when i saw the thread title and the 'problem', it's like you've shot yourself in the foot and calling 911 saying that someone shot you LOL ,just joking, hope you find the answer,good luck