Devicemapper directory shows huge amount of disk space usage

Hello,

I have a CentOS 7 machine with docker installed on it.

$ docker --version
Docker version 18.09.0, build 4d60db4

I have 3 containers deployed on it. The root disk capacity for the cent OS is only of 12 GB, but the following files show disk usage way above that capacity available. How is this possible? What all data gets stored in these files? How are these files used by docker?

$ sudo ls -alh /var/lib/docker/devicemapper/devicemapper
total 3.2G
drwx------. 2 root root 4.0K Nov 20 17:05 .
drwx------. 5 root root 4.0K Nov 20 17:05 …
-rw-------. 1 root root 100G Nov 23 09:02 data
-rw-------. 1 root root 2.0G Nov 23 09:01 metadata

Thanks
Bhushan Pathak