diff --git a/.gitignore b/.gitignore
index 4e0aca0..36784d7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 vendor
 bin
+debug
 *.json
 
 Manifest
diff --git a/Makefile b/Makefile
index fb57953..1b88cc8 100644
--- a/Makefile
+++ b/Makefile
@@ -31,3 +31,8 @@ example:
 	@echo '```' >> EXAMPLE.md
 	@curl -s localhost:9633/metrics | grep smartctl >> EXAMPLE.md
 	@echo '```' >> EXAMPLE.md
+
+collect_fake_json:
+	-mkdir debug
+	-rm -f debug/*json
+	sudo ./collect_fake_json.sh
diff --git a/collect_fake_json.sh b/collect_fake_json.sh
index 87ed1c7..1b8abb4 100755
--- a/collect_fake_json.sh
+++ b/collect_fake_json.sh
@@ -2,5 +2,5 @@
 
 for device in $(smartctl --scan | awk '{ print $1}')
 do
-  smartctl --json --xall $device | jq > $(basename $device).json
+  smartctl --json --xall $device | jq > debug/$(basename $device).json
 done
diff --git a/Dockerfile b/docker/Dockerfile
similarity index 100%
rename from Dockerfile
rename to docker/Dockerfile
diff --git a/config.yaml b/docker/config.yaml
similarity index 100%
rename from config.yaml
rename to docker/config.yaml
diff --git a/docker-entrypoint.sh b/docker/docker-entrypoint.sh
similarity index 100%
rename from docker-entrypoint.sh
rename to docker/docker-entrypoint.sh
diff --git a/main.go b/main.go
index 4c769b4..6e36426 100644
--- a/main.go
+++ b/main.go
@@ -26,10 +26,13 @@ func (i SMARTctlManagerCollector) Describe(ch chan<- *prometheus.Desc) {
 func (i SMARTctlManagerCollector) Collect(ch chan<- prometheus.Metric) {
 	info := NewSMARTctlInfo(ch)
 	for _, device := range options.SMARTctl.Devices {
-		json := readData(device)
-		info.SetJSON(json)
-		smart := NewSMARTctl(json, ch)
-		smart.Collect()
+		if json, err := readData(device); err == nil {
+			info.SetJSON(json)
+			smart := NewSMARTctl(json, ch)
+			smart.Collect()
+		} else {
+			logger.Error(err.Error())
+		}
 	}
 	info.Collect()
 }
diff --git a/readjson.go b/readjson.go
index 39141e1..fb8935e 100644
--- a/readjson.go
+++ b/readjson.go
@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"io/ioutil"
+	"os"
 	"os/exec"
 	"strings"
 	"time"
@@ -35,7 +36,7 @@ func parseJSON(data string) gjson.Result {
 // Reading fake smartctl json
 func readFakeSMARTctl(device string) gjson.Result {
 	splitted := strings.Split(device, "/")
-	filename := fmt.Sprintf("%s.json", splitted[len(splitted)-1])
+	filename := fmt.Sprintf("debug/%s.json", splitted[len(splitted)-1])
 	logger.Verbose("Read fake S.M.A.R.T. data from json: %s", filename)
 	jsonFile, err := ioutil.ReadFile(filename)
 	if err != nil {
@@ -46,30 +47,93 @@ func readFakeSMARTctl(device string) gjson.Result {
 }
 
 // Get json from smartctl and parse it
-func readSMARTctl(device string) gjson.Result {
+func readSMARTctl(device string) (gjson.Result, bool) {
 	logger.Debug("Collecting S.M.A.R.T. counters, device: %s", device)
 	out, err := exec.Command(options.SMARTctl.SMARTctlLocation, "--json", "--xall", device).Output()
 	if err != nil {
 		logger.Warning("S.M.A.R.T. output reading error: %s", err)
 	}
-	return parseJSON(string(out))
+	json := parseJSON(string(out))
+	rcOk := resultCodeIsOk(json.Get("smartctl.exit_status").Int())
+	jsonOk := jsonIsOk(json)
+	return json, rcOk && jsonOk
 }
 
 // Select json source and parse
-func readData(device string) gjson.Result {
+func readData(device string) (gjson.Result, error) {
 	if options.SMARTctl.FakeJSON {
-		return readFakeSMARTctl(device)
+		return readFakeSMARTctl(device), nil
 	}
 
-	if value, ok := jsonCache[device]; ok {
-		// logger.Debug("Cache exists")
-		if time.Now().After(value.LastCollect.Add(options.SMARTctl.CollectPeriodDuration)) {
-			// logger.Debug("Cache update")
-			jsonCache[device] = JSONCache{JSON: readSMARTctl(device), LastCollect: time.Now()}
+	if _, err := os.Stat(device); err == nil {
+		cacheValue, cacheOk := jsonCache[device]
+		timeToScan := false
+		if cacheOk {
+			timeToScan = time.Now().After(cacheValue.LastCollect.Add(options.SMARTctl.CollectPeriodDuration))
+		} else {
+			timeToScan = true
 		}
-	} else {
-		// logger.Debug("Cache not exists")
-		jsonCache[device] = JSONCache{JSON: readSMARTctl(device), LastCollect: time.Now()}
+
+		if timeToScan {
+			json, ok := readSMARTctl(device)
+			if ok {
+				jsonCache[device] = JSONCache{JSON: json, LastCollect: time.Now()}
+				return jsonCache[device].JSON, nil
+			}
+			return gjson.Parse("{}"), fmt.Errorf("smartctl returned bad data for device %s", device)
+		}
+		return gjson.Parse("{}"), fmt.Errorf("Too early collect called for device %s", device)
 	}
-	return jsonCache[device].JSON
+	return gjson.Parse("{}"), fmt.Errorf("Device %s unavialable", device)
+}
+
+// Parse smartctl return code
+func resultCodeIsOk(SMARTCtlResult int64) bool {
+	result := true
+	if SMARTCtlResult > 0 {
+		bits := fmt.Sprintf("%08b", SMARTCtlResult)
+		// logger.Debug("Return code: %d: %s", SMARTCtlResult, bits)
+		if bits[0] == '1' {
+			logger.Error("Command line did not parse.")
+			result = false
+		}
+		if bits[1] == '1' {
+			logger.Error("Device open failed, device did not return an IDENTIFY DEVICE structure, or device is in a low-power mode")
+			result = false
+		}
+		if bits[2] == '1' {
+			logger.Warning("Some SMART or other ATA command to the disk failed, or there was a checksum error in a SMART data structure")
+		}
+		if bits[3] == '1' {
+			logger.Warning("SMART status check returned 'DISK FAILING'.")
+		}
+		if bits[4] == '1' {
+			logger.Warning("We found prefail Attributes <= threshold.")
+		}
+		if bits[5] == '1' {
+			logger.Warning("SMART status check returned 'DISK OK' but we found that some (usage or prefail) Attributes have been <= threshold at some time in the past.")
+		}
+		if bits[6] == '1' {
+			logger.Warning("The device error log contains records of errors.")
+		}
+		if bits[7] == '1' {
+			logger.Warning("The device self-test log contains records of errors. [ATA only] Failed self-tests outdated by a newer successful extended self-test are ignored.")
+		}
+	}
+	return result
+}
+
+// Check json
+func jsonIsOk(json gjson.Result) bool {
+	messages := json.Get("smartctl.messages")
+	// logger.Debug(messages.String())
+	if messages.Exists() {
+		for _, message := range messages.Array() {
+			if message.Get("severity").String() == "error" {
+				logger.Error(message.Get("string").String())
+				return false
+			}
+		}
+	}
+	return true
 }
diff --git a/smartctl.go b/smartctl.go
index 24930ae..6e3f8e6 100644
--- a/smartctl.go
+++ b/smartctl.go
@@ -34,12 +34,12 @@ func NewSMARTctl(json gjson.Result, ch chan<- prometheus.Metric) SMARTctl {
 		family: strings.TrimSpace(smart.json.Get("model_family").String()),
 		model:  strings.TrimSpace(smart.json.Get("model_name").String()),
 	}
-	logger.Verbose("Collecting metrics from %s: %s, %s", smart.device.device, smart.device.family, smart.device.model)
 	return smart
 }
 
 // Collect metrics
 func (smart *SMARTctl) Collect() {
+	logger.Verbose("Collecting metrics from %s: %s, %s", smart.device.device, smart.device.family, smart.device.model)
 	smart.mineExitStatus()
 	smart.mineDevice()
 	smart.mineCapacity()
diff --git a/smartctl_exporter.yaml b/smartctl_exporter.yaml
index 798037b..3e33048 100644
--- a/smartctl_exporter.yaml
+++ b/smartctl_exporter.yaml
@@ -1,7 +1,7 @@
 smartctl_exporter:
   bind_to: "[::1]:9633"
   url_path: "/metrics"
-  fake_json: yes
+  fake_json: no
   smartctl_location: /usr/sbin/smartctl
   collect_not_more_than_period: 20s
   devices:
@@ -11,3 +11,9 @@ smartctl_exporter:
   - /dev/sdd
   - /dev/sde
   - /dev/sdf
+  - /dev/sdg
+  - /dev/sdh
+  - /dev/sdi
+  - /dev/sdj
+  - /dev/sdk
+  - /dev/sdl