diff -r 733714f4dc24 -r 2889e2596bd6 usr/src/lib/libzfs/common/libzfs_status.c
--- a/usr/src/lib/libzfs/common/libzfs_status.c	Sun May 20 02:46:39 2012 -0500
+++ b/usr/src/lib/libzfs/common/libzfs_status.c	Mon May 21 12:11:39 2012 -0700
@@ -18,8 +18,10 @@
  *
  * CDDL HEADER END
  */
+
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012 by Delphix. All rights reserved.
  */
 
 /*
@@ -214,6 +216,20 @@
 		return (ZPOOL_STATUS_VERSION_NEWER);
 
 	/*
+	 * Unsupported feature(s).
+	 */
+	if (vs->vs_state == VDEV_STATE_CANT_OPEN &&
+	    vs->vs_aux == VDEV_AUX_UNSUP_FEAT) {
+		nvlist_t *nvinfo;
+
+		verify(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_LOAD_INFO,
+		    &nvinfo) == 0);
+		if (nvlist_exists(nvinfo, ZPOOL_CONFIG_CAN_RDONLY))
+			return (ZPOOL_STATUS_UNSUP_FEAT_WRITE);
+		return (ZPOOL_STATUS_UNSUP_FEAT_READ);
+	}
+
+	/*
 	 * Check that the config is complete.
 	 */
 	if (vs->vs_state == VDEV_STATE_CANT_OPEN &&
@@ -300,7 +316,7 @@
 	/*
 	 * Outdated, but usable, version
 	 */
-	if (version < SPA_VERSION)
+	if (SPA_VERSION_IS_SUPPORTED(version) && version != SPA_VERSION)
 		return (ZPOOL_STATUS_VERSION_OLDER);
 
 	return (ZPOOL_STATUS_OK);