The following directory /var/lib/registry/docker/registry/v2/blobs/sha256 may be filling up with abandoned, unused docker blobs setting off an alert for /var exceeding the monitoring threshold for filesystems.
In the Gitlab web interface, on the Registry tab, when you click on the "delete" button, only the image tag is actually deleted, and the data itself does not go anywhere and continues to take up space on the hard disk.
A similar problem is observed if the docker image is created with the same tag (for example, latest) — and this is common for the CI process. In this case, when building a new sample, the old one is not deleted (as expected), it simply loses the tag (latest).
For example, the image actually has 2 versions stored on the hard disk:
ls /data/registry/docker/registry/v2/repositories/project/repo-name/_manifests/tags/
1.73.67 2.66.2 2.67.1 2.70.5 2.71.8 2.72.12 2.72.9 2.73.4 2.73.8 2.74.11 2.74.14 2.74.17 latest
2.65.3 2.66.3 2.70.3 2.71.6 2.72.10 2.72.13 2.