diff --git a/PVE/Storage/RBDPlugin.pm b/PVE/Storage/RBDPlugin.pm
index 9e84266..7b1ab1b 100644
--- a/PVE/Storage/RBDPlugin.pm
+++ b/PVE/Storage/RBDPlugin.pm
@@ -494,6 +494,10 @@ sub activate_volume {
     return 1 if !$scfg->{krbd};
 
     my ($vtype, $name, $vmid) = $class->parse_volname($volname);
+    my $pool =  $scfg->{pool} ? $scfg->{pool} : 'rbd';
+
+    my $path = "/dev/rbd/$pool/$name";
+    return if -b $path;
 
     my $cmd = &$rbd_cmd($scfg, $storeid, 'map', $name);
     run_rbd_command($cmd, errmsg => "can't mount rbd volume $name");
diff --git a/changelog.Debian b/changelog.Debian
index b27ad47..6fe4896 100644
--- a/changelog.Debian
+++ b/changelog.Debian
@@ -2,6 +2,8 @@ libpve-storage-perl (4.0-21) unstable; urgency=medium
 
   * rbd: skip unmap if device is not mapped
 
+  * rbd: make activate_volume idempotent
+
  -- Proxmox Support Team <support@proxmox.com>  Thu, 10 Sep 2015 10:43:35 +0200
 
 libpve-storage-perl (4.0-20) unstable; urgency=medium