Parallel in node.js (example with async and co https://github.com/visionmedia/co)

async.copy.js

#!/usr/bin/env node

var fs = require('fs');
var async = require('async');

async.parallel([
  copyFile.bind(null, 'resources/file1.txt', 'resources/file1_copy.txt'),
  copyFile.bind(null, 'resources/file2.txt', 'resources/file2_copy.txt'),
  copyFile.bind(null, 'resources/file3.txt', 'resources/file3_copy.txt')
], function (err, results) {
  if(err) {
    console.error('There was an error copying files', err);
    throw err;
  }

  console.log('copied %d files', results.length);
})

function copyFile (source, dest, callback) {
  fs.createReadStream(source)
    .on('error', callback)
    .pipe(fs.createWriteStream(dest))
    .on('error', callback)
    .on('finish', callback)
}

co.copy.js

#!/usr/bin/env node

var fs = require('fs');
var co = require('co');
var thunkify = require('thunkify');

var copy = thunkify(copyFile);

co(function *() {
  var a = copy('resources/file1.txt', 'resources/file1_copy.txt');
  var b = copy('resources/file2.txt', 'resources/file2_copy.txt');
  var c = copy('resources/file3.txt', 'resources/file3_copy.txt');
  var results = yield [a, b , c];
  console.log('copied files', results);
})()

function copyFile (source, dest, callback) {
  fs.createReadStream(source)
    .on('error', callback)
    .pipe(fs.createWriteStream(dest))
    .on('error', callback)
    .on('finish', callback)
}