Hard drives fail! There is no way around it. It's hardware and nothing lasts forever, so how do you recover from losing your precious photos, data, etc? There are various ways from external disks to cloud storage, expensive vs cheap, you just have to figure out what is best for your situation and your budget. I will describe my setup, and understand this is what I built over time so it is a modular approach.
1 5TB Lacie Rugged external HD
1 WD MyBook Duo Thunderbolt Drive (6TB as Raid1 with 3TB useable)
Synology DS416Play NAS (11TB Useable (2x6TB 2x3TB)
Backblaze Cloud Backup
I have the 5TB Lacie and 6TB WD MyBook connected directly to my 2015 iMac. With the help of BackBlaze, my data from the 5TB Lacie is backed up to the BackBlaze cloud. Since I do all of my photo editing and store my catalogs on that drive, it gets backed up real time to the cloud. The drawback is that it may take days to recover it by downloading from the cloud. If you can afford to wait a few days while your data downloads then this is the easiest and cheapest option as you can get an 8TB single external HD for $140 on Amazon. I recommend the Seagate STGY8000400 Desktop 8TB External Hard Drive HDD - USB 3.0 for PC Laptop & Mac. BackBlaze is $50 a year per computer with unlimited storage (https://www.backblaze.com/cloud-backup.html). You can back up any external drive that is physically attached to your computer. Unfortunately NAS devices are not backed up.
Since I don't want to wait days to download and I use a mac, I use ChronoSync to sync my data from my 5TB Lacie to my 6TB WD MyBook. ChronoSync is a one time price of $49.99 with lifetime updates (https://www.econtechnologies.com/chronosync/overview.html). It has a scheduler, so I set it to sync from my drives once a week. This allows me restore my work pretty quickly, like hours vs days. I don't do editing every day so my chance of losing any work is small. If I find myself doing more editing, I can always set a new schedule to sync daily. I feel my WD MyBook is kind of small, so I will be upgrading it in the near future and will post my recommended 2 drive enclosure at the end.
I have a crap ton of data that I don't use on a regular basis such as at least a TB of photography training videos, plugins, brushes, overlays etc so I purchased a synology nas to store it all. I like the synology nas because their proprietary raid system allows me to add larger drives without losing data while still being protected. I currently have a 4 bay nas with 2x3TB drives and 2x6TB drives. I will be replacing the 3TB drives soon with either 8 or 10TB drives. Unfortunately it would be way expensive to back this up to the cloud, however other than a fire, or other natural disaster or event where all the drives are destroyed my data is still redundant within the nas device. I can lose one drive with no problem and can replace that drive with the same size or larger. If the actual nas enclosure fails, I can just buy a new one and replace the drives from the old into the new, they just have to go back in the same order. At least that is what the synology website says :) When I replace my drives, either in my nas or my attached raid enclosure, I always replace them with pro red nas drives. They are meant to do read and write disk access 24x7 and should last 5 years before failure. The synology nas definitely alerts you when drives are starting to fail so you should rarely have one just crash. I do recommend you do regular checkups to make sure your disks are not getting bad sectors.
I mentioned upgrading my WD MyBook. While you can replace the drives in it, I think because it is so old that I am limited to how big I can go. I have been doing some research and just ordered a TERRAMASTER D2-310 USB Type C External Hard Drive RAID Enclosure USB3.0 (5Gbps) 2-Bay RAID Storage Support RAID 0/1/Single (Diskless) on amazon for $155. I do have 2 4TB drives I am going to stick in it to do some testing, but I will eventually be getting 2x Seagate IronWolf 12TB NAS Internal Hard Drive HDD – 3.5 Inch SATA 6Gb/s 7200 RPM 256MB Cache for $321 each on Amazon.
I hope this has been useful, please comment below with any questions or comments.