Why Is an Image Uploaded Through the Client to SWR Different in Size From One Uploaded Through the SWR Console?

Symptom

Assume that a nginx image of v2.0.0 is created on the local Docker client. The docker images command is run to query SIZE of the image. The size is 22.8 MB.

$ docker images
REPOSITORY                         TAG             IMAGE ID       CREATED         SIZE
nginx                              v2.0.0          22f2bf2e2b4f   9 days ago      22.8MB

1. Run the docker push command to upload the image to SWR. The size of the image is 9.5 MB.
2. On the local Docker client, pack the image into a .tar package. Download the nginx.tar package to the local host, and upload the package to SWR. The size of the package is 23.2 MB.

The size of the image uploaded through the client is different from that of the image uploaded through the SWR console.

Cause Analysis

Image layers are compressed into .tgz packages when images are uploaded to SWR through the client, whereas when they are uploaded through the SWR console, they are only packed without being compressed. Therefore, the same image will be of different sizes when it is uploaded in these two different ways.