diff --git a/dashboards/victoriametrics.json b/dashboards/victoriametrics.json
index 9f173981a..d4a1facc7 100644
--- a/dashboards/victoriametrics.json
+++ b/dashboards/victoriametrics.json
@@ -14,7 +14,7 @@
       "type": "grafana",
       "id": "grafana",
       "name": "Grafana",
-      "version": "6.3.5"
+      "version": "6.4.4"
     },
     {
       "type": "panel",
@@ -65,7 +65,7 @@
   "gnetId": 10229,
   "graphTooltip": 0,
   "id": null,
-  "iteration": 1572208904768,
+  "iteration": 1573078001588,
   "links": [
     {
       "icon": "doc",
@@ -96,6 +96,7 @@
   "panels": [
     {
       "collapsed": false,
+      "datasource": "${DS_PROMETHEUS}",
       "gridPos": {
         "h": 1,
         "w": 24,
@@ -109,6 +110,7 @@
     },
     {
       "content": "<div style=\"text-align: center; font-size: 2em\">$version</div>",
+      "datasource": "${DS_PROMETHEUS}",
       "description": "",
       "gridPos": {
         "h": 3,
@@ -470,6 +472,7 @@
     },
     {
       "collapsed": false,
+      "datasource": "${DS_PROMETHEUS}",
       "gridPos": {
         "h": 1,
         "w": 24,
@@ -1253,13 +1256,106 @@
         "alignLevel": null
       }
     },
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": "${DS_PROMETHEUS}",
+      "description": "Slow queries according to `search.logSlowQueryDuration` flag, which is `5s` by default.",
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 8,
+        "w": 12,
+        "x": 0,
+        "y": 43
+      },
+      "id": 60,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": false,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "links": [],
+      "nullPointMode": "null",
+      "options": {
+        "dataLinks": []
+      },
+      "percentage": false,
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [],
+      "spaceLength": 10,
+      "stack": false,
+      "steppedLine": false,
+      "targets": [
+        {
+          "expr": "sum(rate(vm_slow_queries_total{job=\"$job\"}[5m]))",
+          "format": "time_series",
+          "hide": false,
+          "intervalFactor": 1,
+          "legendFormat": "slow queries rate",
+          "refId": "A"
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "Slow queries",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "decimals": null,
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
     {
       "collapsed": false,
+      "datasource": "${DS_PROMETHEUS}",
       "gridPos": {
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 43
+        "y": 51
       },
       "id": 14,
       "panels": [],
@@ -1279,7 +1375,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 44
+        "y": 52
       },
       "id": 10,
       "legend": {
@@ -1378,7 +1474,7 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 44
+        "y": 52
       },
       "id": 34,
       "legend": {
@@ -1483,7 +1579,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 52
+        "y": 60
       },
       "id": 30,
       "legend": {
@@ -1573,7 +1669,7 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 52
+        "y": 60
       },
       "id": 36,
       "legend": {
@@ -1663,7 +1759,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 60
+        "y": 68
       },
       "id": 53,
       "legend": {
@@ -1753,7 +1849,7 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 60
+        "y": 68
       },
       "id": 55,
       "legend": {
@@ -1829,6 +1925,182 @@
         "alignLevel": null
       }
     },
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": "${DS_PROMETHEUS}",
+      "description": "The number of on-going merges in storage nodes.  It is expected to have high numbers for `storage/small` metric.",
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 8,
+        "w": 12,
+        "x": 0,
+        "y": 76
+      },
+      "id": 62,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": true,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "nullPointMode": "null",
+      "options": {
+        "dataLinks": []
+      },
+      "percentage": false,
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [],
+      "spaceLength": 10,
+      "stack": false,
+      "steppedLine": false,
+      "targets": [
+        {
+          "expr": "sum(vm_active_merges{job=\"$job\"}) by(type)",
+          "legendFormat": "{{type}}",
+          "refId": "A"
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "Active merges",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "decimals": 0,
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": "${DS_PROMETHEUS}",
+      "description": "The number of rows merged per second by storage nodes.",
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 8,
+        "w": 12,
+        "x": 12,
+        "y": 76
+      },
+      "id": 64,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": true,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "nullPointMode": "null",
+      "options": {
+        "dataLinks": []
+      },
+      "percentage": false,
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [],
+      "spaceLength": 10,
+      "stack": false,
+      "steppedLine": false,
+      "targets": [
+        {
+          "expr": "sum(rate(vm_rows_merged_total{job=\"$job\"}[5m])) by(type)",
+          "legendFormat": "{{type}}",
+          "refId": "A"
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "Merge speed",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "decimals": 0,
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
     {
       "aliasColors": {},
       "bars": false,
@@ -1842,7 +2114,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 68
+        "y": 84
       },
       "id": 58,
       "legend": {
@@ -1923,11 +2195,12 @@
     },
     {
       "collapsed": false,
+      "datasource": "${DS_PROMETHEUS}",
       "gridPos": {
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 76
+        "y": 92
       },
       "id": 46,
       "panels": [],
@@ -1947,7 +2220,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 77
+        "y": 93
       },
       "id": 44,
       "legend": {
@@ -2046,13 +2319,14 @@
       "bars": false,
       "dashLength": 10,
       "dashes": false,
+      "datasource": "${DS_PROMETHEUS}",
       "fill": 1,
       "fillGradient": 0,
       "gridPos": {
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 77
+        "y": 93
       },
       "id": 57,
       "legend": {
@@ -2141,7 +2415,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 85
+        "y": 101
       },
       "id": 47,
       "legend": {
@@ -2231,7 +2505,7 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 85
+        "y": 101
       },
       "id": 42,
       "legend": {
@@ -2320,7 +2594,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 93
+        "y": 109
       },
       "id": 48,
       "legend": {
@@ -2400,7 +2674,7 @@
     }
   ],
   "refresh": "30s",
-  "schemaVersion": 19,
+  "schemaVersion": 20,
   "style": "dark",
   "tags": [],
   "templating": {
@@ -2483,5 +2757,5 @@
   "timezone": "",
   "title": "VictoriaMetrics",
   "uid": "wNf0q_kZk",
-  "version": 3
-}
+  "version": 4
+}
\ No newline at end of file
diff --git a/deployment/docker/docker-compose.yml b/deployment/docker/docker-compose.yml
index 5c5e57e88..d06c1f083 100644
--- a/deployment/docker/docker-compose.yml
+++ b/deployment/docker/docker-compose.yml
@@ -35,7 +35,7 @@ services:
     restart: always
   grafana:
     container_name: grafana
-    image: grafana/grafana:6.3.5
+    image: grafana/grafana:6.4.4
     entrypoint: >
       /bin/sh -c "
       cd /var/lib/grafana &&
diff --git a/deployment/docker/provisioning/datasources/datasource.yml b/deployment/docker/provisioning/datasources/datasource.yml
index 4e3c9177e..43467512d 100644
--- a/deployment/docker/provisioning/datasources/datasource.yml
+++ b/deployment/docker/provisioning/datasources/datasource.yml
@@ -5,10 +5,10 @@ datasources:
       type: prometheus
       access: proxy
       url: http://prometheus:9090
-      isDefault: false
+      isDefault: true
 
     - name: VictoriaMetrics
       type: prometheus
       access: proxy
       url: http://victoriametrics:8428
-      isDefault: true
+      isDefault: false