diff --git a/sys/fs/nfs/nfs.h b/sys/fs/nfs/nfs.h
index 2661e1270cdb..75439e370dba 100644
--- a/sys/fs/nfs/nfs.h
+++ b/sys/fs/nfs/nfs.h
@@ -176,6 +176,17 @@ struct nfsd_nfsd_args {
 	int	maxthreads;	/* maximum service thread count */
 };
 
+/*
+ * NFSDEV_MIRRORSTR - string of digits that number the DSs 0->999.
+ * (To support more than 1000 DSs on an MDS, this needs to be increased.)
+ * NFSDEV_MAXMIRRORS - Maximum # of mirrors for a DS.
+ * (Most will only have a single mirror, but this setting allows up to 3.)
+ * NFSDEV_MAXVERS - maximum number of NFS versions supported by Flex File.
+ */
+#define	NFSDEV_MIRRORSTR	3
+#define	NFSDEV_MAXMIRRORS	4
+#define	NFSDEV_MAXVERS		4
+
 /*
  * Arguments for use by the callback daemon.
  */