fixes #1450 (#1472)

CHANGELOG.md

@@ -36,6 +36,7 @@ should now look like:
 
 ### Bugfixes
 
+- [#1472](https://github.com/influxdata/telegraf/pull/1472): diskio input plugin: set 'skip_serial_number = true' by default to avoid high cardinality.
 - [#1426](https://github.com/influxdata/telegraf/pull/1426): nil metrics panic fix.
 - [#1384](https://github.com/influxdata/telegraf/pull/1384): Fix datarace in apache input plugin.
 - [#1399](https://github.com/influxdata/telegraf/issues/1399): Add `read_repairs` statistics to riak plugin.

plugins/inputs/system/disk.go

@@ -92,8 +92,8 @@ var diskIoSampleConfig = `
   ## disk partitions.
   ## Setting devices will restrict the stats to the specified devices.
   # devices = ["sda", "sdb"]
-  ## Uncomment the following line if you do not need disk serial numbers.
-  # skip_serial_number = true
+  ## Uncomment the following line if you need disk serial numbers.
+  # skip_serial_number = false
 `
 
 func (_ *DiskIOStats) SampleConfig() string {
@@ -151,6 +151,6 @@ func init() {
 	})
 
 	inputs.Add("diskio", func() telegraf.Input {
-		return &DiskIOStats{ps: &systemPS{}}
+		return &DiskIOStats{ps: &systemPS{}, SkipSerialNumber: true}
 	})
 }