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: '',
    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
}...

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.