In computing world, data are archived mainly using tape drives and hard disks with redundancy, but how are TV shows and movie reels preserved? This question talks about the format but what about the physical medium for shows and movies shot decades ago.
Until they can get around to digitising all the back catalogue, they're stored in their original format - film, video tape etc, in huge data storage warehouses.
From BBC Archives
BBC Archives has over 1.5 million items in the Television Collection. The earliest recordings are on film and date from the end of 1946. Greater coverage of Television output is kept from 1948 and covers multiple formats including 35mm and 16mm film, 1” Videotape, Betacam, Umatic, D3 as well as digital files.
The Television Collection is stored within environmentally safe conditions in vaults where both temperature and humidity levels are monitored and regulated.
BBC Archives is digitising many of its older tape formats to digital files and storing them in a digital archive.
For a fuller explanation, start from What's in the BBC Archives? then work through the links below.
Originals (film, video) are sometimes stored in underground in climate stable environments (SF Gate). One such location used heavily is a company called "Underground Vaults" in Kansas.
From the SF Gate article.
Plus, the mine naturally retains a year-round temperature and humidity considered nearly ideal for preserving paper and film.
So it is that secret government documents, hospital X-rays and generations of records from insurance providers, banks and international corporations all end up here, under a heartland wheat field.
So it is too that the original prints and discarded outtakes of Hollywood history -- from Charlie Chaplin to "Gone With the Wind" to "Star Wars" and beyond -- have landed in a town where the skyline consists of a peeling grain elevator.
A YouTube video showing various items in these secure archives is located here.
Additionally, the American Masters documentary "Johnny Carson: King of Late Night" has video of the shelves of "The Tonight Show" archives at approximately 4 minutes and 15 seconds (in the Kansas location).