Backup tool for external drives (like tapes)?

After upgrading my server, I have a bunch of spare drives. Both the on-site and off-site server are now completely full (Node 804) and adding more is a huge pain in the ass.

At same time, I also got the dreaded Google mail regarding storage usage. So even though I have a 1:1 replica off-site, I still want to make additional backups. I was thinking of treating old drives as tapes meaning the backup software keeps a metadata database online, showing which drive needs to be connected to restore a specific file / validate backups.

I know LTO backup tools work like this but is there anytrhing like this for drives? Pref. a web UI, docker and open-source. Thanks.