diff --git a/interface/ri_tk_cmd.py b/interface/ri_tk_cmd.py
index 27a67d2..0920b20 100644
--- a/interface/ri_tk_cmd.py
+++ b/interface/ri_tk_cmd.py
@@ -313,16 +313,20 @@ level - raid level (0/1/5)
 devs  - raid component devices
 '''
     # all devs shall have same size. 
+    unit=ri_data.Partition.unit
+    sz=99999999999
     for p in ri_data.Partition.list:
-        if p.device == devs[0]:
-            sz = p.size
-            break
+        if p.device in devs:
+            if  float(p.size[:-len(unit)])< float(sz):
+                sz = float(p.size[:-len(unit)])
     if level == '0':
-        return len(devs)*sz
+        sz=sz*len(devs)
+        return "%d%s"%(sz,unit)
     elif level == '1':
-        return sz
+        return "%d%s"%(sz,unit)
     elif level == '5':
-        return sz*(len(devs)-1)
+        sz=sz*(len(devs)-1)
+        return "%d%s"%(sz,unit)
 
 def raid_device_add():
     ''' add a new raid device '''