There was a day, I was really wondering what consumes most of my system storage. After a while, I find out this very interesting to improve storage space for Android phones.
Connect ADB to the phone (you can either use USB cable or Wifi, event Bluetooth works, too), then access to the phone shell.
$ adb shell
and list the sizes of all directories at root.
$ du -sh *
1.9G data <--- gotcha
Oh, this line is bugging to my eyes
Access to it and query size again, I’ve found this one is killing my phone indeed.
Too many logs on this directory, I remove ‘em all, and system storage gets more space to work again.
If you’ve ever faced the issues with storages, you can try those steps.