I want to share a fairly optimal set up to use Lightroom with my NAS, a Synology in RAID 6 (but any redundancy is ok).
The key points:
1. The LR catalog must be on the local drive and not on the network drive, but I still want full automatic back up and hourly snapshots. Any decent NAS lets you set something similar to dropbox, where the files are local, but they are automatically synced to the NAS with full redundancy. Recent changes are also stored on the NAS and can be recovered at will. This set up also has the advantage that I can share my LR catalog with any machine on my network for work: in other words I can import images on my Macbook, edit on my iMac, prepare a print on my Macbook again. As long as I remember to close LR when I'm done, everything works flawlessly, all changes are shared automatically across every computer. It also, means, for example, that I can simply import locally and eventually see my images replicated on the NAS.
2. I keep recent images on my local drive that is automatically synced with the NAS through the dropbox-like shared folder that I mentioned. I can access the images with the highest bandwidth available and they are still synced automatically to my NAS and available on every computer on my network. For example, when I'm in the field, I import images on my Macbook; when I come back home, as soon as the Macbook joins the local network, all the images are automatically synched with the NAS without any intervention. For critical images, I can sync from remote, again automatically.
3. Older images are stored on a shared network folder that is only stored on the NAS (not locally). Slower access, but no need to use precious local disk space. This images can still be accessed from remote if I'm on location, but it would be pretty slow (still doable in case of emergency). All remote communication goes through encrypted HTTPS channels, so it's secure.
4. Both the dropbox-like folder and the shared network folder are snapshotted every hour: in other words I can recover from the NAS anything every hour for the last year or so. It saved me more times than I can count at the expense of some limited NAS storage (the system is very efficient).
5. Both the dropbox-like folder and the shared network folder are backed up automatically every night on an external USB disk connected to the NAS.
6. The shared network folder is constantly backed up automatically in the cloud (I use Amazon drive which is free for Prime users): when I move older images from the local dropbox-like folder to the shared folder on the NAS, the images are automatically copied to the cloud. The Lightroom catalog is also automatically backed up in the cloud.
I must stress the point that from the point of view of the user (me and my wife's business share the same system), once set up, all the redundancy happens automatically without user intervention: we use Lightroom as usual with the only caveat of closing it once the work is done and copying old images to the shared network folder. My mantra is that any time there is a manual step involved, it can and will go wrong. Our set up is like working locally with Lightroom, but shared on all our machines and with full redundancy and backups happening automatically.
I can go more in details if anyone wants to try to replicate our set up. Hope it helps.