I actually bought just one new 6TB HDD and repurposed an older 3TB one as a redundancy drive for mirroring most critical data using a simple rsync cron job (no need for realtime mirroring of media files that are write-once), plus another old 1 TB drive just because. I haven't run out of storage yet and I have automated download/sharing for OpenStreetMap and some Linux distros which takes up half a TB or so, but I plan on expanding the array using MergerFS and SnapRAID when the need arises.
The rest is just SMB shares, Navidrome, Jellyfin, DLNA and FTP. Remote access from outside my local network is done via Tailscale VPN.