diff -ruN anaconda-13.21.195.upstream/storage/devices.py updates/storage/devices.py
--- anaconda-13.21.195.upstream/storage/devices.py	2012-12-10 15:40:04.000000000 -0800
+++ updates/storage/devices.py	2013-12-02 20:19:32.000000000 -0800
@@ -1879,7 +1879,7 @@
 
         # TODO: validate peSize if given
         if not self.peSize:
-            self.peSize = 4.0   # MB
+            self.peSize = 32.0   # MB
 
         if not self.exists:
             self.pvCount = len(self.parents)
@@ -2249,6 +2249,11 @@
         used = sum(lv.vgSpaceUsed for lv in self.lvs) + self.snapshotSpace
         used += self.reservedSpace
         free = self.size - used
+
+        pad = self.peSize * 2 * len(self.pvs)
+        if free >= pad:
+            free -= pad
+
         log.debug("vg %s has %dMB free" % (self.name, free))
         return free