.TP
.BI flock
Enable full distributed
-.BI flock (2)
+.BR flock (2)
support, coherent across all client nodes also using this mount option. This
is useful if applications need coherent userspace file locking across multiple
-client nodes, but also imposes communications overhead in order to maintain
-locking consistency between client nodes.
+client nodes, has no measurable performance impact in modern (2.x) versions of
+Lustre, is therefore the recommended mode, and is enabled by default in Lustre
+2.12.3 and newer.
.TP
.BI localflock
Enable local
with the
.B flock
option, and can be used for applications that depend on functioning
-.BI flock (2)
+.BR flock (2)
but run only on a single node.
.TP
.BI noflock
Disables
-.BR flock(2)
-support entirely, and is the default option. Applications calling
-.BR flock(2)
+.BR flock (2)
+support entirely. Applications calling
+.BR flock (2)
will get an
.B ENOSYS
-error. It is up to the administrator to choose either the
-.B localflock
-or
-.B flock
-mount option based on their requirements. It is possible to mount clients
+error. It is possible to mount clients
with different options, and only those mounted with
.B flock
will be coherent amongst each other.