Copying files to/from VMWare guest OS is slow: an alternate approach

I really like VMWare VIX API’s CopyFileFromGuestToHost and CopyFileFromHostToGuest. These automatically copy a single file or an entire directory tree. Easy. Unfortunately I am copying large (150-300 Mb) files to/from a VMWare guest OS and it’s taking an hour to copy a hundred megs. I bet VMWare API was developed by Russian developers, so it’s probably sending UTF-8 encoded bytes in Russian via SOAP. You might remember that I am writing a tool that lets one test a cross-product of installers and virtual machine snapshots: three MSIs multipled by twenty snapshots equals days of file copying! It’s not going to work.

I posted a question about this in VMWare Communities and got a satisfactory response: I don’t think there is a workaround. We are aware of the issue (we run in to it internally) and hope to fix it in a future release.

In the meantime, I need a short term solution.

I decided to try and map the remote drive and use a simple File.Copy. The first challenge is to find out the remote server’s IP address. VMWare exposes guest OS variables, including the ip, so I’ve extended VMWareTasks to support those.

/// <summary>
/// Environment, guest and runtime variables
/// </summary>
/// <param name="name">name of the variable</param>
[IndexerName("Variables")]
public string this[string name]
{
  get
  {
    VMWareJob job = new VMWareJob(_vm.ReadVariable(_variableType, name, 0, null));
    object[] properties = { Constants.VIX_PROPERTY_JOB_RESULT_VM_VARIABLE_STRING };
    return job.Wait<string>(properties, 0, VMWareInterop.Timeouts.ReadVariableTimeout);
  }

  set
  {
    VMWareJob job = new VMWareJob(_vm.WriteVariable(_variableType, name, value, 0, null));
    job.Wait(VMWareInterop.Timeouts.WriteVariableTimeout);
  }
}

Here’s the IP address of a powered-on VM.

virtualMachine.GuestVariables["ip"];

We can make up a network path out of a local one.

public string PathToNetworkPath(string ip, string value)
{
  return string.Format(@"\\{0}\{1}", ip, value.Replace(":", "$"));
}

Mapping a network drive is implemented in mpr.dll with WNetAddConnection2. A wrapper class will do the job.

public class NetworkDrive
{
  [DllImport("mpr.dll")]
  public static extern int WNetAddConnection2(ref NETRESOURCE lpNetResource, string lpPassword, string UserName, int dwFlags);

  [StructLayout(LayoutKind.Sequential)]
  public struct NETRESOURCE
  {
    public int dwScope;
    public int dwType;
    public int dwDisplayType;
    public int dwUsage;
    public string lpLocalName;
    public string lpRemoteName;
    public string lpComment;
    public string lpProvider;
  }

  private const int RESOURCETYPE_DISK = 0x1;

  private string _localName;
  private string _remoteName;

  public NetworkDrive(string remoteName)
  {
    _remoteName = remoteName;
  }

  public NetworkDrive(string remoteName, string localName)
  {
    _remoteName = remoteName;
    _localName = localName;
  }

  public string LocalName
  {
    get { return _localName; }
    set { _localName = value; }
  }

  public string RemoteName
  {
    get { return _remoteName; }
    set { _remoteName = value; }
  }

  public void MapNetworkDrive(string username, string password)
  {
    NETRESOURCE netResource = new NETRESOURCE();
    netResource.dwScope = 2;
    netResource.dwType = RESOURCETYPE_DISK;
    netResource.dwDisplayType = 3;
    netResource.dwUsage = 1;
    netResource.lpRemoteName = _remoteName;
    netResource.lpLocalName = _localName;
    int rc = WNetAddConnection2(ref netResource, password, username, 0);
    if (rc != 0)
    {
      throw new Win32Exception(rc);
    }
  }
}

Let’s put it all together.

public void CopyFileFromGuestToHost(string guestPath, string hostPath)
{
  string guestNetworkPath = PathToNetworkPath(_ip, guestPath);
  NetworkDrive guestNetworkDrive = new NetworkDrive(Path.GetPathRoot(guestNetworkPath));
  guestNetworkDrive.MapNetworkDrive(_username, _password);
  File.Copy(guestNetworkPath, hostPath, true);
}

The last thing that remains to be done to make the new copy compatible is to also copy directories and subdirectories. That’s left as an exercise to the reader.

Daniel Doubrovkine

Copying files to/from VMWare guest OS is slow: an alternate approach vmware

Copying files to/from VMWare guest OS is slow: an alternate approach