For years I've gotten by simply doing periodic manual backups. For a while I used CDs, then DVDs, then spare hard drives. I currently have a pair of 3TB Toshiba DT01ACA300 drives that I bought about a year and a half ago since they were super cheap ($80 each) and the internet majority was saying that these were high quality Hitachi drives under a different name and therefor a great buy. Sadly I'm starting to see that there are more reports of these having issues than most other drives (check newegg reviews) and just today I ran Hard Disk Sentinel and saw that it showed 95% health with 8 weak sectors! Just a few weeks ago I had no weak or bad sectors at all. My previous drive, a Samsung F1 1TB is still working flawlessly after 7+ years of use, so I'm pretty bummed about this Toshiba. I got the second drive so that I could periodically make a 1:1 copy of my current drive. I don't really do anything "mission critical" so to speak, but I do keep a lot of files that I'd be really upset to lose (pictures, music, backups for family members, tons of files for random projects and vintage computing archives). I do also have an old 1TB WD Green drive that I have been filling with a second copy of the most critical long-term stuff (family pictures, etc.) and I keep that in my fire safe.
Anyway, long story short, this has reminded me of the mortality of storage devices (again), but this time I really want to do something about it. I'd also like to be able to keep a good solid backup of my wife's laptop because she does use that for her online business. Most of the critical stuff is online, but all of her working files and product photos are stored on her system, and I periodically do a backup of that. Having the ability to also backup Android devices over our home network would be a huge bonus as well, as we take pictures and do things with our phones and tablets frequently, and I'd prefer to not have to pay a monthly fee for Google drive for each one.
My number one concern is cost, as I can't justify buying a $300 NAS when I've gotten by without one for nearly 20 years of having my own computer (and I still have all of the files from the very beginning). I have lots of parts and other fairly decent systems to use for a DIY NAS, so that would be highly preferred.
Second concern would be ease of use, as I'm not that well versed in this kind of thing. I have minimal exposure to Linux (beyond Android) and no experience with setting up servers (beyond Minecraft).
I'd like to just have everything NEW on each partition of each computer backed up somehow either automatically at the end of the day, or on command with a couple clicks. Deleted file recovery isn't a huge deal (I'm already very careful with this and never had a problem with it), and there will generally be not much changing each day... some new pictures, some new files, etc. But if a drive starts losing data or corrupting files, that needs to be covered.
I see basically two different ways to go with this, depending on how complicated or expensive they are:
(1)Ideally I'd like to know that I have a backup of the state my computer is in at the end of the day. If my hard drive starts to die, or my SSD suddenly bricks itself, I'd like to know that I have a fairly easy way to restore everything from that drive\partition to a new drive without losing anything. Basically, a mirror image of my partitions (on a few different computers), updated easily with only the things that have changed at the end of the day (why rewrite 2TB of the same data when only 400MB has changed?) My concern with this method is that the backups would be inaccessible, obscure files on some mystery box that I can't just open up and recover specific things from if needed. If this is too complex or network\system intensive, I'd gladly settle for the following.
(2)A simpler automated file\directory based backups that accomplishes the same thing, minus the ability to just mirror a partition back to its previous state. For example, backup whatever directories I want... my desktop, my document folders, Steam folders etc. with the files that have changed at the end of the day, but if my SSD bricks itself I still have to reinstall Windows, vs just using a full system image. This doesn't bother me that much, as this is an extreme case and I don't currently do anything that would make my life end if I had to spend an evening setting things back up. As long as my files that I can't replace are safe somewhere, that's my main concern.
I have a fairly decent router (Netgear Nighthawk X4 R7500v2) with Gigabit Ethernet run through my house and available in a few rooms, so connectivity should be okay (nothing fancy though). If the system is flexible enough to also be useful for other things at the same time to help justify running all day, that'd be a bonus. We don't really have much need for a file server (set up a basic one several times and we've never really used it much) but if the option was there for that or home automation applications, it wouldn't hurt.