draw.io for Confluence Server 5.3 offers a first look at the mass Gliffy import option, currently in beta. For now, we recommend trying it out on a copy of your Confluence spaces before applying in production. If the import fidelity of any import is not good enough, please email the Gliffy diagram (it's an attachment on the page) to email@example.com.
Navigate to the draw.io plugin admin screen, CONFLUENCE_PATH/admin/drawioConfig.action, and click on the "Diagram Import" tab. You'll see this:
You'll be told how many pages contain Gliffy diagrams. To start the import click "Import" and "OK" on the confirmation dialog. Importing will take some time if you have a lot of diagrams. On a low-end server, allow 1 minute per 10 diagrams as a rule of thumb.
Once the import is complete, all your Gliffy diagrams will be replaced. The import is all or nothing, if there are problems during the process, no diagrams will import. We also do not delete the original Gliffy diagram from the page attachments.