diff --git a/weed-fs/src/pkg/topology/data_center.go b/weed-fs/src/pkg/topology/data_center.go
index 022f733cc..92e8b0055 100644
--- a/weed-fs/src/pkg/topology/data_center.go
+++ b/weed-fs/src/pkg/topology/data_center.go
@@ -1,6 +1,10 @@
 package topology
 
-import (
-
-)
+import ()
 
+type DataCenterId uint32
+type DataCenter struct {
+	Id      DataCenterId
+	racks   map[RackId]*Rack
+	ipRange IpRange
+}
diff --git a/weed-fs/src/pkg/topology/ip_range.go b/weed-fs/src/pkg/topology/ip_range.go
new file mode 100644
index 000000000..e7bd5a0fe
--- /dev/null
+++ b/weed-fs/src/pkg/topology/ip_range.go
@@ -0,0 +1,11 @@
+package topology
+
+import (
+
+)
+
+
+type IpRange struct {
+  inclusives   []string
+  exclusives   []string
+}
diff --git a/weed-fs/src/pkg/topology/node.go b/weed-fs/src/pkg/topology/node.go
index 2a556e5ad..91f9a1373 100644
--- a/weed-fs/src/pkg/topology/node.go
+++ b/weed-fs/src/pkg/topology/node.go
@@ -1,18 +1,17 @@
 package topology
 
-import (
-
-)
+import ()
 
+type NodeId uint32
 type VolumeId uint32
 type VolumeInfo struct {
-  Id   VolumeId
-  Size int64
+	Id   VolumeId
+	Size int64
 }
 type Node struct {
-  volumes     map[VolumeId]VolumeInfo
-  volumeLimit int
-  Ip          string
-  Port        int
-  PublicUrl   string
+	volumes     map[VolumeId]VolumeInfo
+	volumeLimit int
+	Ip          string
+	Port        int
+	PublicUrl   string
 }
diff --git a/weed-fs/src/pkg/topology/rack.go b/weed-fs/src/pkg/topology/rack.go
index 69895a243..3e06ea3af 100644
--- a/weed-fs/src/pkg/topology/rack.go
+++ b/weed-fs/src/pkg/topology/rack.go
@@ -1,10 +1,10 @@
 package topology
 
-import (
-
-)
+import ()
 
+type RackId uint32
 type Rack struct {
-  nodes     map[uint64]*Node
-  IpRanges   []string
+	Id      RackId
+	nodes   map[NodeId]*Node
+	ipRange IpRange
 }
diff --git a/weed-fs/src/pkg/topology/topology.go b/weed-fs/src/pkg/topology/topology.go
new file mode 100644
index 000000000..7db3d0e32
--- /dev/null
+++ b/weed-fs/src/pkg/topology/topology.go
@@ -0,0 +1,9 @@
+package topology
+
+import (
+
+)
+
+type Topology struct {
+  datacenters     map[DataCenterId]*DataCenter
+}