Running cheap, redundant PCs (or occasionally scrapped commercial servers) as a servers since 1994. In the 1980s backups were a few floppies (5.25", 3.5", 3"). Then for a while tape cartridges.
Now backups are on SATA HDDs in USB 3.0 enclosures. Added a 10T drive for €140 last week and swapped the 4T in workstation (additional to SSD) for the 6T in backup-box which had less than 2 months run time. CD/DVD are rubbish for backups because they fade. Also Flash USB fades. An HDD might be OK in a drawer for 50 years if you still have the interface, so update backup HW occasionally.
Storage is very cheap. The cheapest 1950 mains table radio in today's money is about €300. That buys a lot of storage.
rsync is used to update "server" (a PC dumped by a local office, they trusted me to wipe HDDs, which lives in concrete shed at back of garden) and then to cheap laptops (< €350 and < €160).
Backup, Backup. Cloud/OneDrive/Dropbox/Google is a sharing tool, not a backup.