We get quite a few RFPs (requests for proposals) from companies, so they can compare offerings fairly. More than often we see that there are high expectations of the storage amounts needed. I always try to get in contact with the people making these estimations to try to see what's up, do they really need 8TB? Or what's the case? Well, here are a few things that might help you when considering the amount of storage you need.
Just adding up current storage (cd's, dvd's, USB sticks & hard-drives) seems like an OK rough estimate. However, hardly any of these storage devices are filled to the brim, so better to actually check how much of these devices and carriers are actually full.Considering duplicate content in your estimates is very important. Sometimes entire folders are duplicated or still exist on the source media (for example, the original disk still exists but the files have been copied to the local file server too). But also files that have been renamed or reused can generate large amounts of duplicate data. (Bynder has a very easy 'find duplicate' feature to eliminate duplicate content once added).
Consider how long it will take to actually upload a terabyte of data. You'll soon find that most companies physically won't be able to handle terabytes of files due to limited network speeds.
How many files need to be readily available? Are all your files used often? Or is a large part just archive material? Often we see the latter. In that case it can save money by using cheaper (but with availability lag) long-term archive storage space. Compare it to keeping some of your things in the attic rather than on the kitchen table.
On the other hand, keep in mind there a few things that use more storage than you maybe expected... Think about the growing use of HD or even UltraHD video material. Plain 'old' Digital Photography itself is also going up in megapixels.