diff --git a/lib/format/ataraid/pdc.c.raid10_failure b/lib/format/ataraid/pdc.c

index b0bb652..8b14d71 100644

--- a/lib/format/ataraid/pdc.c

+++ b/lib/format/ataraid/pdc.c

@@ -490,7 +490,9 @@ devices(struct raid_dev *rd, void *context)

 	if (context && pdc->raid.type != PDC_T_SPAN)

 		*((uint64_t *) context) += rd->sectors;

-	return pdc->raid.total_disks;

+	return is_raid10(pdc) ?

+	       pdc->raid.total_disks / 2 :

+	       pdc->raid.total_disks;

 }

 static int