What is the reason for growing container in GBs when its a single file change?

Hi,

We are using the docker daemon with base image of 30G for oracle docker image (25 GB) and did some changes in tnsnames.ora file.
We did export of the same and imported with a new image name. The size was close to 28 GB.

If it was done via save and load, the size was close to 48 GB.

Any idea about the bigger difference in sizes , when its a small file change?

**docker version**

Client version: 1.6.2
Client API version: 1.18
Go version (client): go1.4.2
Git commit (client): ba1f6c3/1.6.2
OS/Arch (client): linux/amd64
Server version: 1.6.2
Server API version: 1.18
Go version (server): go1.4.2
Git commit (server): ba1f6c3/1.6.2
OS/Arch (server): linux/amd64