diff --git a/diskutil.py b/diskutil.py
index 68f49fbc..885c62f2 100644
--- a/diskutil.py
+++ b/diskutil.py
@@ -298,6 +298,9 @@ def getDiskDeviceSize(dev):
         return int(__readOneLineFile__("/sys/block/%s/device/block/size" % dev))
     elif os.path.exists("/sys/block/%s/size" % dev):
         return int(__readOneLineFile__("/sys/block/%s/size" % dev))
+    else:
+        raise Exception("%s not found as %s or %s" % (dev, "/sys/block/%s/device/block/size",
+                                                      "/sys/block/%s/size"))
 
 def getDiskSerialNumber(dev):
     # For Multipath nodes return info about 1st slave
diff --git a/product.py b/product.py
index c07e12ee..72dbe766 100644
--- a/product.py
+++ b/product.py
@@ -559,13 +559,31 @@ def findXenSourceBackups():
         b = None
         try:
             b = util.TempMount(p, 'backup-', ['ro'], 'ext3')
-            if os.path.exists(os.path.join(b.mount_point, '.xen-backup-partition')):
-                backup = XenServerBackup(p, b.mount_point)
-                logger.log("Found a backup: %s" % (repr(backup),))
-                if backup.version >= XENSERVER_MIN_VERSION and \
-                        backup.version <= THIS_PLATFORM_VERSION:
-                    backups.append(backup)
-        except:
+            if not os.path.exists(os.path.join(b.mount_point, '.xen-backup-partition')):
+                raise StopIteration()
+
+            backup = XenServerBackup(p, b.mount_point)
+            logger.log("Found a backup: %s" % (repr(backup),))
+
+            if backup.version < XENSERVER_MIN_VERSION:
+                logger.log("findXenSourceBackups: ignoring, platform too old: %s < %s" %
+                           (backup.version, XENSERVER_MIN_VERSION))
+                raise StopIteration()
+            if backup.version > THIS_PLATFORM_VERSION:
+                logger.log("findXenSourceBackups: ignoring later platform: %s > %s" %
+                           (backup.version, THIS_PLATFORM_VERSION))
+                raise StopIteration()
+            if not os.path.exists(backup.root_disk):
+                logger.error("findXenSourceBackups: PRIMARY_DISK=%r does not exist" %
+                             (backup.root_disk,))
+                raise StopIteration()
+
+            backups.append(backup)
+
+        except StopIteration:
+            pass
+        except Exception as ex:
+            logger.log("findXenSourceBackups caught exception for partition %s: %s" % (p, ex))
             pass
         if b:
             b.unmount()