/scratch filesystems are relatively small and expensive. Unused data will be migrated out (razor) or deleted (trestles).
Razor: Top level subdirectories under /scratch/$USER are searched for files modified less than 60 days ago. If none are found, the subdirectories are migrated to either /storage/$USER/ if no name conflict or /storage/$USER/scratch if there is a name conflict. This may erroneously move read-only data that doesn't hit the “modified” flag, but that data should be in /storage/$USER.
Trestles: Top level subdirectories under /scratch (there are no $USER directories, only job directories) are deleted after 60 days.
Please Note razor scratch storage will be reconfigured to act like trestles within the next two months. Job scratch directories are auto-created and available now on razor the same as trestles.