This section of the forum is now closed; we are working on a new support model for WDL that we will share here shortly. For Cromwell-specific issues, see the Cromwell docs and post questions on Github.
If I understand correctly, call-caching works by copying the files from a previous workflow provided that the script, input are the exact same. But since WDL is copying file it is taking up too much disk space. Is there a way to make it do hard or soft linking instead?