MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
When data is cloned, the following directories and files are created for internal use. They should not be modified.
#clone: Contains internal clone files used by the cloning operation. Created in the directory that data is cloned to.
#ib_archive: Contains internally archived log files, archived on the donor during the cloning operation.
*.#clonefiles: Temporary data files created on the recipient while data is removed from the recipient data directory and new data is cloned during a remote cloning operation.