Ask HN: organising historical personal data

Any experience organising personal files dating from decades back, much of it useless but not irrelevant? Entire filesystems, backups, backups of backups, stored in CDs, hard disks, as zip files, email, etc?

The purpose is to be able to answer questions such as: where's that picture? Is this the last revision? Are there any backups of those files? And to essentially keep a canonical copy of each item (for some useful definition of item).

Simple search won't solve it because data will be repeated several times. A file duplicate finder would need some additional information about how things are going to be organized.