diff --git a/weed/stats/metrics.go b/weed/stats/metrics.go
index a60cda290..13ab3bae1 100644
--- a/weed/stats/metrics.go
+++ b/weed/stats/metrics.go
@@ -77,6 +77,14 @@ var (
 			Help:      "Number of volumes or shards.",
 		}, []string{"collection", "type"})
 
+	VolumeServerReadOnlyVolumeGauge = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Namespace: "SeaweedFS",
+			Subsystem: "volumeServer",
+			Name:      "read_only_volumes",
+			Help:      "Number of read only volumes.",
+		}, []string{"collection", "type"})
+
 	VolumeServerMaxVolumeCounter = prometheus.NewGauge(
 		prometheus.GaugeOpts{
 			Namespace: "SeaweedFS",
@@ -122,6 +130,7 @@ func init() {
 	Gather.MustRegister(VolumeServerRequestHistogram)
 	Gather.MustRegister(VolumeServerVolumeCounter)
 	Gather.MustRegister(VolumeServerMaxVolumeCounter)
+	Gather.MustRegister(VolumeServerReadOnlyVolumeGauge)
 	Gather.MustRegister(VolumeServerDiskSizeGauge)
 
 	Gather.MustRegister(S3RequestCounter)
diff --git a/weed/storage/store.go b/weed/storage/store.go
index d5d59235a..72a388379 100644
--- a/weed/storage/store.go
+++ b/weed/storage/store.go
@@ -200,6 +200,7 @@ func (s *Store) CollectHeartbeat() *master_pb.Heartbeat {
 	maxVolumeCount := 0
 	var maxFileKey NeedleId
 	collectionVolumeSize := make(map[string]uint64)
+	collectionVolumeReadOnlyCount := make(map[string]uint8)
 	for _, location := range s.Locations {
 		var deleteVids []needle.VolumeId
 		maxVolumeCount = maxVolumeCount + location.MaxVolumeCount
@@ -219,6 +220,9 @@ func (s *Store) CollectHeartbeat() *master_pb.Heartbeat {
 			}
 			fileSize, _, _ := v.FileStat()
 			collectionVolumeSize[v.Collection] += fileSize
+			if v.IsReadOnly() {
+				collectionVolumeReadOnlyCount[v.Collection] += 1
+			}
 		}
 		location.volumesLock.RUnlock()
 
@@ -243,6 +247,10 @@ func (s *Store) CollectHeartbeat() *master_pb.Heartbeat {
 		stats.VolumeServerDiskSizeGauge.WithLabelValues(col, "normal").Set(float64(size))
 	}
 
+	for col, count := range collectionVolumeReadOnlyCount {
+		stats.VolumeServerReadOnlyVolumeGauge.WithLabelValues(col, "normal").Set(float64(count))
+	}
+
 	return &master_pb.Heartbeat{
 		Ip:             s.Ip,
 		Port:           uint32(s.Port),