keyword everything!!! As are Collections and Smart Collections in LR. I use XXClone for my backups, but I still manage with the PhotoShop equivalent of LR. XXClone just duplicates the hard drive contents onto another-it doesn't index them or make it easy as pie to find everything. If your LR catalog is maintained on that initial disc, it's copied onto the backup. Networking can work, even with LR. You'll need to have your drives in a secure hard drive enclosure and that probably should be hard mounted to prevent bumping and getting tossed around.
HOWEVER... I also have the feeling you aren't talking about a double back up, but just to get them off your main computer and archive. In which case I'd still do the INITIAL clone onto your new hard drive. That way if your working hard drive fails you have EVERYTHING backed up. Hard drives have a life expectancy of between 2 and 3 years depending on the use of them. After the initial clone you can then continue to add to that drive, but don't use clone because it will overwrite on the back up with what is on the current working hard drive. If you delete the originals off your working drive it will also remove from the back up.
If your main LR cataloging contains a catalog for that NAS or RAID or... it will be able to go to the network and pull the contents from that external drive. Just be sure to keep your LR catalog updated.
Cataloging is the largest power of LR.
Here is some info from Adobe on it.
DPBestflow is a study funded by the Library of Congress for the preservation of imaging and has a PLETHORA of resources on this. It was their primary focus, but as you know cataloging, preservation and archiving is a huge part of workflow from start to finish. The website is so incredibly indepth that you can spend days on there. It's worth it. If you ever get to attend a seminar put on by DPBestflow DO IT! It's SO worth while.
Welcome | Digital Photography Best Practices and Workflow | dpBestflow
This is their section on Disk Configurations
Disk Configurations | dpBestflow And this is their file management launch
File Management | dpBestflow