No sorry, there is no plug-in for Synology to download patches (would be cool though - anyone?). However, I've been fiddling around with vSphere UMDS and wanted to have the patches downloaded to my Synology NAS box. And through the Synology webservices act as a patch store - AND IT WORKS :-).

Setup is quite easy, running a Windows 2008 machine. Now there are excellent tutorials and manuals available online to install UMDS, so I'm not going to repeat that.

On your Synology, create a new virtual host (I've called mine VUM). This creates a new folder inside your web folder. I've also shared this folder, so UMDS can download patches to there. 

Now install UMDS (now there are excellent tutorials on how to configure this, so I'm not repeating that), for the patch location - accept the default, since you cannot install to a share. However, after installation change the patch store location with:

vmware-umds.exe -S --patch-store

Now copy the old file structure to that share.

You could have also changed the downloadConfig.xml, but I do not recommend that, you can screw up XML files quite easily.

I also remove the downloads for ESX3.5 and 4.0 since I only running 5.0 which saves some space. Start the download of the patches with:

vmware-umds.exe -D

The only thing left to do is make sure your VUM servers are using the repository and it works great. I updated a couple of ESXi 5.0 servers and I didn't need any fiddling around with mime types on the Synology. Remediation just works.

An other thing I noticed: VUM doens't locally cache the packages - which is great. You can ignore that '120GB' space for patch location during installation, just have enough space on your Synology.

As for scheduling the packages - I made this VM really 'small' since it is only downloading, not a tough job. However, to free up valuable resources I scheduled the VM to boot every night, during VM start-up a boot script kicks off the download, after download it shuts down. Cool huh .