I use syncthing to sync almost everything across my computer, laptop (occasional usage), server (RAID1), old laptop (powered up once every month or so), and a few other devices (that only get a small subset of my data, though). On the computer, laptop, and server, I have btrfs snapshots (snapper). Overall, this works very well, I always have 4+ copies of my data in 2+ geographical locations.
I met someone that was throwing out old memory modules. Literally boxes full of DDR, DDR2 modules. I got quite excited, hoping to upgrade my server’s memory. Yeah, DDR2 only goes up to 2GiB. So I am stuck with 2×2GiB. But I am only using 85% of that anyways, so it’s fine.