Extending storage module size?

Additionally, I've encountered an issue when using the fs module. Specifically, when I call the fs.appendFileSync(filename, data); method and I repeatedly execute this code block within a setInterval function, I'm experiencing issues with missing or inconsistent file writes. Could you please assist me in resolving this when you have the time?

function downloadData(filename) {
  require('http').get("http://xxx.com/pic/"+filename, function(res) {
    var i = 0;
    res.on('data', function(data) {
      i+=1;
      console.log('download:' + filename + " chunk =>" + i + '...');
      fs.appendFileSync(filename, data);
    });
    res.on('close', function(data) {
      console.log("Connection closed");
      console.log(fs.readdirSync());
    });
  });
}