Ingesting HiTS2015 takes a very long time in Gen 3; after 30 minutes on lsst-devl01, it had not yet finished the preliminary import used to create an independent repository. This is unexpected, since of the affected datasets (calibs, crosstalk, defects, refcats, templates), only templates should scale up in size with the overall dataset size, and only defects and refcats should require file copies. For comparison, the entire import of CI-HiTS2015 takes 30 seconds.
Run tests comparing the current Gen 2 and Gen 3 behavior to confirm whether the latter is much slower. If so, track down the cause.