I am running out of storage space in my back up drives. My solution is to increase the capacity. This fits with my workflow. It's been suggested to me, however, to zip the files. Does anyone have an opinion or experience? My files are stored as RAW with some processed as TIFF or PSD. Occasionally when I want to post or put on my website I use JPG. I do go back and use the archive RAW when working on projects.
Like you, I store my files in the native format. I have never used zips for backups. For one ting, it requires the use of additional software (Unzip, 7-zip, etc) just to extract the file contents (at least on a Windows PC).
For my backup drives, I use the G-Technology 6TB G-DRIVE USB G1 USB 3.0 Hard Drive ($189) but there are also 10 TB models now available ($299). Since the use is backup, I really don't care about the speed for Photoshop, etc. For live editing, my image editing PC is equipped with a 4 TB SSD (2 x 2 TB RAID0) which is fast.
These drives are inexpensive enough that you can just purchase additional drives when you run out of space. So I have my ancient images on other drives. Yes I am old fashioned and don't have a NAS system 🙂 Mainly because they are noisy and I don't have a place for remote (to my office) installation and I don't need 24/7 access to backups.
I second John - storage is cheap. I'd be curious how much disk space you'd save with .zip files, but I wouldn't think the juice is worth the squeeze - it would be a pain in the keister to manage.
I do have a NAS, but only because it was a (nice) gift, and I periodically backup to that, plus a near-time, automatic backup always runs to another direct-attached drive.
Most important, I auto-backup to an online service. I didn't see mention of that in your question, but I believe this is the most important part of my backup strategy.
Agree with John and Lloyd - from experiments in the past, Nikon Raw files zipped (or compressed using other compression tech) yields savings of 2-3%, so pretty much negligible and not worth the hassle.
As Lloyd mentioned, storage is inexpensive these days. I use both external disks via USB and internal disks accessed via a Dock such as this - https://www.amazon.com/Sabrent-External-Duplicator-Function-EC-HD2B/dp/B0759567JT/ref=sr_1_3?keywords=hard+drive+Dock&qid=1585154461&sr=8-3
These sorts of Docks are available in both USB and Thunderbolt, like this Thunderbolt Dock - https://www.amazon.com/HighPoint-Dual-Bay-Thunderbolt-RocketStor-5212/dp/B00DJ3YEH0/ref=sr_1_3?keywords=thunderbolt+hard+drive+Dock&qid=1585154572&sr=8-3
Thunderbolt Docs are more expensive relative to USB Docks but are very fast. For static storage and backup, speed isn't strictly necessary, so the simple USB Dock may work well. I use typically NAS-rated disks in the external dock, like this one - https://www.amazon.com/Red-4TB-NAS-Hard-Drive/dp/B00EHBERSE/ref=sr_1_3?keywords=Western+Digital+REd&qid=1585154692&sr=8-3
Various sizes and speeds are available. For backup, 5400 RPM disks are fine. The dock allows easily removing the drive and storage them off site, if desired.
Finally, the best backup solution for Mac that I've found and can heartily recommend is Carbon Copy Cloner - https://bombich.com
Finally, a Raid Array enclosure with hot-swap capability is also a good solution to consider. OWC sell the Mercury line that I've had decent results with.
I concur with John, Lloyd and Raaj. Over the years my Mac-based system has evolved to an external Thunderbolt 4-drive enclosure, configured as 2-disk pairs, one backing up the other, each disk now 6TB. All Western Digital drives. Next capacity jump would probably be to 10TB drives, as the price point seems reasonable at the moment.
I do keep my current year files on the SSD in the computer itself, for the slight speed advantage. At the end of the calendar year I move these files to the 4-drive enclosure (using Lightroom, of course).
Tapping into my accountant anal-retentive self, I also have a Drobo unit to which everything is backed up nightly. And then there's the three portable WD drives, backed up to monthly, for remote storage.
I haven't yet done the on-line back up; smart idea, just not there at the moment.
If you are a Mac user, Carbon Copy Cloner is the ONLY software to use. Very flexible and totally reliable.