I'm on Windows so I use Everything as my search and VVV (Virtual Volumes View) for an offline searchable database. I also keep copies of TV show episode and apperances lists from Wikipedia.
With my drive organization, which is a variation on animal, vegetable. mineral*, I can find anything within seconds as long as I know something about it. More below.
*Animal, vegetable, mineral is based on the idea that everything can be primarily catagorized into one of those three catagories. So in my case, if I know a movie is by a certain director, stars a certain actress or was a certain type of show, I can go directly to that drive or folder.
I don't use RAID because I like to keep my drives separate and just do a 1:1 swapout when one fails without any rebuild time. This does leave a lot of unused slack space and I do have to upgrade my drive size every so often, but by that time I'm ready to retire my active drives to backup anyway.
I have two backups. An exact set of mirror drives and my second backup is spread over 3 & 4TB drives. Unfortunately I don't have anywhere to store them physically offsite and could is too expensive for my 200TB raw hoard. Everything is verified after copy and every few years, re-verify the integrity of the files with ViceVersa to ensure they're bit of for bit accurate. Unfortunately, I didn't save the HASH(es) the first go around, but am now doing it during the re-verify and initial copy.
Note: Always copy, never move your files and always verify! Odd things can happen if you move! There are those that say, correctly that a move on the same drive just rewrites the location to the File Allocation Table, but I still never move unless the file is completely unimportant.
For finding duplicates, Czwaka is highly recommended here for all file types. I've been using Video Duplicator for years and will continue to use it since I have the Pro version.
My drive organization, is 20 dedicated drives ranging from 8-14TB. Each drive/set of drives is for:
Directors - Alpha by name
Actresses - Alpha by name
Music - Sub categorized into groups/soloists and type of show (Reality, Variety, Special)
Variety Shows
Reality Shows
Specials/Documentaries/Shorts/Collections
Movies with sequels - Regardless of director