Backing up your NAS

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Ok, so you have your NAS and you have built it with some redundancy (RAID). But what if the whole thing dies (the system motherboard)? Well, at least you will need a spare unit. Nonetheless, having all your data on a single device that can die anytime does not seem like a good idea, so some sort of backup plan is needed. One possible idea is to have a second NAS unit that will be kept in sync with the main one, so that you can switch it back to be the main one in case of a failure of the main unit. Not cheap but a workable solution. However, certain risks like a robbery or a fire need to be covered, so keeping the two NAS at the same location is not a good idea. 

So one possible solution is to have the backup system remote and to connect it to the office system VPN, so backups can take place. This opens up an interesting networking problem if the VPN server is not run by the NAS box, as the VPN addressing space is going to be different than the office network addressing space. That would mean the local NAS may not be able to connect to the remote NAS even though it is connected to the VPN server and thus can access the local network. 

There are a couple of problems here: 

  1. The VPN network may not be reached from computers on the office network unless a static route is added to their routing tables (otherwise, they will try to reach the VPN network through the gateway, as they believe it is out there on the Internet).
  2. The remote NAS connecting to the VPN may get a different IP address every time it reconnects, but that makes it a moving target. We need to fix that by assigning a fixed address to it, which we can do in the VPN server configuration.
Once these two problems are addressed, the remote backup can start, and hopefully, our systems will last a long time. 

Alternatively, an odd but perhaps simpler solution may be to have the office NAS always connected to the VPN server; this way, we can avoid problem 1 altogether. 

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