Major:

change replication_type to ReplicaPlacement, hopefully cleaner code
works for 9 possible ReplicaPlacement
xyz
x : number of copies on other data centers
y : number of copies on other racks
z : number of copies on current rack
x y z each can be 0,1,2

Minor:
weed server "-mdir" default to "-dir" if empty

go/storage/volume_info.go

@@ -5,7 +5,7 @@ import ()
 type VolumeInfo struct {
 	Id               VolumeId
 	Size             uint64
-	RepType          ReplicationType
+	ReplicaPlacement *ReplicaPlacement
 	Collection       string
 	Version          Version
 	FileCount        int