Lustre-1.6 and Lustre-1.8 series support MDT file-level backup/restore. But such function does not work on Lustre-2.x yet. Because Lustre-2.x introduces Object Index (OI) file for global FID to MDT local identifier mapping, which is different from Lustre-1.6/1.8. Such OI file will become invalid after MDT file-level backup/restore.
This Phase I project will have LFSCK rebuild the OI file after MDT file-level backup/restore to make it workable as Lustre-1.6/1.8 series do.