For my main machine: Sys, 1TB. Games, 4TB (actually 2x 2TB in raid0). Backups and misc: 10TB. Daily backups, g/f/s for sys, and incremental daily with monthly full for games.

Then I have all my media and actual files on a nas, along with the desktop, documents, downloads synced between all machines; any files that are for storage and drive images (for machines with only 1 drive and cannot manage images locally) get stored here too. 2x 10TB.

Then those drives are in raid1, are under btrfs with snapshot abilities, are backed up to a 8TB external every month, and unplugged after a successful backup to avoid a ransomware attack scenario. This drive is actively cooled to prevent overheating with hours of read/write activity. Every night, critical files are also backed up to two different off-site data storage services, on different continents.

I got tired of data loss 15 years ago, and now I horde everything, but it's all for a purpose. Game saves, stories, photos, archived projects long forgotten, and so much more.