Chris Wahl wrote a good blog post about the VAAI-NAS plugin some days ago. I really recommend to read this posting. Because of his article, I will only describe the installation of the plugin. You can download the plugin on the Synology homepage for free.
There are two ways to install the plugin: With the vSphere Update Manager (VUM) and a host extension baseline, or with ESXCLI.
Plugin installation using the vSphere Update Manager
First of all, we need to import the plugin (host extension) to the patch repository. Open the vSphere C# client, switch to the “Home” screen and click “Update Manager” under “Solutions and Applications”. Switch to the “Patch Repository” tab and click “Import Patches”.