Export whether SMART is available for a device

[ben-z]

Currently, we only check whether smart_status.passed is true. If it's false, then assume SMART did not pass. However, there's another possibility that the device doesn't support SMART at all.

smartctl_exporter/smartctl.go

Line 462 in 7482daf

smart.json.Get("smart_status.passed").Float(),

I have a MegaRAID device that exhibits this behaviour:

root@wato-derek2:~# smartctl /dev/sda -a
smartctl 7.2 2020-12-30 r5155 [x86_64-linux-5.4.119-1-pve] (local build)
Copyright (C) 2002-20, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Vendor:               IBM
Product:              ServeRAID M5015
Revision:             2.13
Compliance:           SPC-3
User Capacity:        47,999,999,803,392 bytes [47.9 TB]
Logical block size:   512 bytes
Logical Unit id:      0x600605b0041170402ad08eba1fe4604f
Serial number:        004f60e41fba8ed02a40701104b00506
Device type:          disk
Local Time is:        Tue Apr 23 02:40:30 2024 EDT
SMART support is:     Unavailable - device lacks SMART capability.

=== START OF READ SMART DATA SECTION ===
Current Drive Temperature:     0 C
Drive Trip Temperature:        0 C

Error Counter logging not supported

Device does not support Self Test logging

{
  "json_format_version": [
    1,
    0
  ],
  "smartctl": {
    "version": [
      7,
      2
    ],
    "svn_revision": "5155",
    "platform_info": "x86_64-linux-5.4.119-1-pve",
    "build_info": "(local build)",
    "argv": [
      "smartctl",
      "/dev/sda",
      "--json",
      "--info",
      "--health",
      "--attributes",
      "--tolerance=verypermissive",
      "--nocheck=standby",
      "--format=brief",
      "--log=error"
    ],
    "exit_status": 0
  },
  "device": {
    "name": "/dev/sda",
    "info_name": "/dev/sda",
    "type": "scsi",
    "protocol": "SCSI"
  },
  "vendor": "IBM",
  "product": "ServeRAID M5015",
  "model_name": "IBM ServeRAID M5015",
  "revision": "2.13",
  "scsi_version": "SPC-3",
  "user_capacity": {
    "blocks": 93749999616,
    "bytes": 47999999803392
  },
  "logical_block_size": 512,
  "serial_number": "004f60e41fba8ed02a40701104b00506",
  "device_type": {
    "scsi_value": 0,
    "name": "disk"
  },
  "local_time": {
    "time_t": 1713854444,
    "asctime": "Tue Apr 23 02:40:44 2024 EDT"
  },
  "temperature": {
    "current": 0,
    "drive_trip": 0
  }
}

There should be a check to see if the smart_status object is available. If it is not, then SMART is not available for the device.