How large is your Lightroom library currently? What kind of increase are you expecting on a yearly basis?
How large are your RAW files on the externals taking up?
Do you have any offsite backups?
I don't know what LR Smart Previews are but I have an idea; I'll look it up.
Are you comfortable with command line at all?
Budget is not a concern really but I don't want to go crazy. I will spend 1-2K to get a lot of future proofing on overdoing my storage. My common-law partner is not a concern either for this.
LR library is stored on my internal SSD and I plan to transfer it back and forth from iMac to rMBP with a USB3 stick with SSD controller so it will be fairly fast.
Other than my RAW files, I will store my iTunes library and about 1TB of movies/video files that I own and I will want to use the space to have clones/backups of my 3 computers (iMac (512GB), 12"rMB (512GB) and 15rMBP (512GB)).
My offsite backups now is taking my USB3 drives and keeping them at work. We have internet caps and no way to get unlimited bandwidth (I have 300GB/month and use it mostly with Netflix so can't use an internet upload).
I will be the only person accessing the files and only from one computer at a time.
My LR Cataloge is ~ 1GB and my Preview file is ~90GB. Smart Previews allow you to edit and even export up to a certain size jpeg without having the RAW files attached.
My RAW files are currently at 4TB and growing much faster than previously which could be about 1TB/yr.
I'm not really comfortable with Command Line...well I have typed in certain commands in the past that I've read online but don't really use it.
Hope that answers most or all of the questions. Really appreciate any help you can provide.
Currently I'm looking at OWC Thunderbay 4 RAID with about 12TB and then deciding whether to run RAID 5 or RAID 0+1 or something else and maybe even another Thunderbay for cloning to. I think if I have that at home I can use up all my USB3 portable Seagate drives as off-site backups. I have a lot of 1TB one and now four 2TB ones.