Mirroring a remote storage

[knfevg]

Hello all.
We got a new NV+ v2 for our small office and we are planning to use it for three needs:
1. Sharing files
2. Backup of laptops
3. "Bringing closer" the corporate shared drive

I know how to do the first 2 things but have no idea about the 3rd one. HEre is the situation: in the HQ there is a storage with a shared "drive" mapped to all computers of all employees. Outside of the HQ this drive is accesbible only when the computer is connected to a VPN (Cisco VPN Client). As we have frequent issues with the internet connection, we would like to keep an up to date copy (syncing maybe once a day, at night) of some of the files on that drive on our local Readynas. How can this be realised?

Thank you,
Evgeny