Some local filesystem consistency verification tools, such as e2fsck for ldiskfs, will add the orphan objects under backend special /lost+found directory. Such directory is invisible to clients. The namespace LFSCK will scan such directory, and for the objects that were visible to clients originally (according to the FID), the namespace LFSCK will move them back to the normal namespace (according to the linkEA) or to the global visible .lustre/lost+found/MDTxxxx/ directory.