.br
.B lfs check <mds|osts|servers>
.br
-.B lfs data_version [-n] \fB<filename>\fR
+.B lfs data_version [-nrw] \fB<filename>\fR
.br
.B lfs df [-ihlv] [--pool|-p <fsname>[.<pool>]] [path]
.br
.B check
Display the status of MDS or OSTs (as specified in the command) or all the servers (MDS and OSTs)
.TP
-.B data_version [-n] <filename>
-Display current version of file data. If -n is specified, data version is read
-without taking lock. As a consequence, data version could be outdated if there
-is dirty caches on filesystem clients, but this will not force data flushes and
-has less impact on filesystem.
+.B data_version [-nrw] <filename>
+Display the current version of file data. If -n is specified, the data version
+is read without taking a lock. As a consequence, the data version could be
+outdated if there are dirty caches on filesystem clients, but this option will
+not force data flushes and has less of an impact on the filesystem. If -r is
+specified, the data version is read after dirty pages on clients are flushed. If
+-w is specified, the data version is read after all caching pages on clients are
+flushed.
-Even without -n, race conditions are possible and data version should be
+Even with -r or -w, race conditions are possible and the data version should be
checked before and after an operation to be confident the data did not change
during it.
+
+The data version is the sum of the last committed transaction numbers of all
+data objects of a file. It is used by HSM policy engines for verifying that file
+data has not been changed during an archive operation or before a release
+operation, and by OST migration, primarily for verifying that file data has not
+been changed during a data copy, when done in non-blocking mode.
.TP
.B getname [-h]|[path ...]
Report all the Lustre mount points and the corresponding Lustre filesystem