+script which is used to provide extra functionality when migrating file
+data between OSTs and has a separate man page. See
+.BR lfs_migrate (1)
+for details.
+.SH MDT MIGRATE OPTIONS
+.TP
+.BR -m , --mdt-index=\fIstart_mdt_index\fR
+Directory will be migrated to MDTs starting with
+.I start_mdt_index
+, or specific MDTs if multiple MDTs are specified in a comma-seperated list.
+This is useful if new MDTs have been added to a filesystem and existing user or
+project directories should be migrated off old MDTs to balance the space usage
+and future metadata workload. If
+.I start_mdt_index
+is set to -1, the MDT will be chosen by space and inode usage.
+.TP
+.BR -c , --mdt-count=\fICOUNT\fR
+Directory will be migrated to
+.I COUNT
+MDTs.
+.TP
+.BR -H , --mdt-hash=\fIHASH_TYPE\fR
+Use
+.I HASH_TYPE
+for the new layout.
+.RS 1.2i
+.TP
+.B all_char (type 1)
+Sum of ASCII characters modulo number of MDTs. This
+provides weak hashing of the filename, and is suitable
+for only testing or when the input is known to have
+perfectly uniform distribution (e.g. sequential numbers).
+.TP
+.B fnv_1a_64 (type 2)
+Fowler-Noll-Vo (FNV-1a) hash algorithm. This provides
+reasonably uniform, but not cryptographically strong,
+hashing of the filename. (default)
+.TP
+.B crush (type 3)
+CRUSH hash algorithm. This is a consistent hash
+algorithm, so minimum sub files need to relocate
+during directory restripe.
+.RE
+.P
+Only the root user can migrate directories. Files that have been archived by
+HSM or are currently opened will fail to migrate, user can run the same migrate
+command again to finish migration when files are ready. Both inode and
+directory entry will be migrated. During migration directory and sub files can
+be accessed like normal ones.
+.TP
+\fIWARNING\fR
+A migrated file or directory will have a new FID, and hence a new inode
+number. As a consequence, files archived by Lustre HSM that depend on
+the FID as the identifier in the HSM archive cannot currently be migrated.
+Having a new inode number may also cause backup tools to consider the
+migrated file(s) to be a new, and cause them to be backed up again.
+.P