In this section you will learn how to get disks information, file system information, disk I/O stats and file system stats:

For function reference and examples we assume, that we imported systeminformation as follows:

const si = require('systeminformation');

Disk Layout, Block Devices and Disks IO

All functions in this section return a promise or can be called with a callback function (parameter cb in the function reference)

const si = require('systeminformation');
si.diskLayout().then(data => console.log(data));

[
  {
    device: '/dev/nvme0n1',
    type: 'NVMe',
    name: 'SAMSUNG xxxxxxxxxxxx-xxxx',
    vendor: 'Samsung',
    size: 1024209543168,
    bytesPerSector: null,
    totalCylinders: null,
    totalHeads: null,
    totalSectors: null,
    totalTracks: null,
    tracksPerCylinder: null,
    sectorsPerTrack: null,
    firmwareRevision: '',
    serialNum: '...serial....',
    interfaceType: 'PCIe',
    smartStatus: 'unknown',
    smartData: {
      json_format_version: [Array],
      smartctl: [Object],
      device: [Object],
      model_name: 'SAMSUNG xxxxxxxxxxxx-xxxx',
      serial_number: '...serial....',             // full structure
      ...                                         // see index.d.ts
    }
  },
  {
    ...
  }
]

const si = require('systeminformation');
si.blockDevices().then(data => console.log(data));

[
  {
    name: 'nvme0n1',
    type: 'disk',
    fsType: '',
    mount: '',
    size: 1024209543168,
    physical: 'SSD',
    uuid: '',
    guid: '',
    label: '',
    model: 'SAMSUNG xxxxxxxxxxxx-xxxx',
    serial: '... serial ...',
    removable: false,
    protocol: 'nvme',
    group: '',
    device: 'nvme0n1'
  },
  {
    ...
  }
]

const si = require('systeminformation');
setInterval(function() {
  si.disksIO().then(data => {
    console.log(data);
  })
}, 1000)

{                           // first call
  rIO: 899825,
  wIO: 932331,
  tIO: 1832156,
  rIO_sec: null,
  wIO_sec: null,
  tIO_sec: null,
  ms: 0
}
{                           // second call
  rIO: 899863,
  wIO: 932331,
  tIO: 1832194,
  rIO_sec: 38.5395537525355,
  wIO_sec: 0,
  tIO_sec: 38.5395537525355,
  ms: 986
}...

File System and File System Stats

const si = require('systeminformation');
si.fsSize().then(data => console.log(data));

[
  {
    fs: '/dev/md2',
    type: 'ext4',
    size: 972577361920,
    used: 59142635520,
    available: 913434726400,
    use: 6.08,
    mount: '/',
    rw: true
  },
  {
    ...
  }
]

const si = require('systeminformation');
si.fsOpenFiles().then(data => console.log(data));

{
  max: 6566555,
  allocated: 1856,
  available: 0
}

const si = require('systeminformation');
setInterval(function() {
  si.fsStats().then(data => {
    console.log(data);
  })
}, 1000)

{                             // first call
  rx: 14015849472,
  wx: 15316003328,
  tx: 29331852800,
  rx_sec: null,
  wx_sec: null,
  tx_sec: null,
  ms: 0
}
{                             // second call
  rx: 14015849472,
  wx: 15316007424,
  tx: 29331856896,
  rx_sec: 0,
  wx_sec: 4083.748753738784,
  tx_sec: 4083.748753738784,
  ms: 1003
}...

Volume GUID (Windows)

On Windows, blockDevices() also returns the volume GUID path of a drive in guid, e.g. \\?\Volume{a6b89b02-753b-4f4b-91e6-5b3b6e290017}\. This is the stable name of a volume - independent of its drive letter - and it is what tools like mountvol expect when a volume is mounted or unmounted. It is read from Win32_Volume and matched to the drive by its letter.

The field stays empty when no volume entry belongs to the drive (e.g. network drives) and on all other platforms. Note that uuid is a different value: it keeps the file system serial number (VolumeSerialNumber) and is unchanged. Volumes without a drive letter (EFI, recovery partitions) are not part of the result, as they are not reported as logical disks.

Getting correct stats values

In disksIO() and fsStats() the results / sec. values (rx_sec, IOPS, ...) are calculated correctly beginning with the second call of the function. It is determined by calculating the difference of transferred bytes / IOs divided by the time between two calls of the function.

The first time you are calling one of this functions, you will get -1 for transfer rates. The second time, you should then get statistics based on the time between the two calls ...

So basically, if you e.g. need a values for filesystem stats stats every second, your code should look like this:

const si = require('systeminformation');

setInterval(function() {
    si.fsStats().then(data => {
        console.log(data);
    })
}, 1000)

Beginning with the second call, you get file system transfer values per second.