In this approach, the files from the data directory of an existing replica set member are directly copied to the replica set member in need of resynchronization. This approach is best in situations where the amount of data is sizeable, and where network communications would be adversely affected following the initial sync approach described in the previous sub section.
Unfortunately, trying to obtain a direct file copy while a mongod instance is running might prove difficult as database files are frequently locked, held open, and contents are changing. Accordingly, you either need to shut down the mongod instance in order to obtain a copy or use external operating system tools to obtain a filesystem snapshot.
Unlike the process of restoring a replica set described earlier in this chapter, you must include the local database in the copy.