Anyone with a collection of CDs, DVDs or Blu-rays will know just how much storage space is needed. A standard CD case is about 1cm thick and DVD cases at least about 1.5 times as thick. 100 CDs in their cases will therefore need about a 1 metre-wide shelf and that is not an especially large collection. Some people may well have thousands!
This is a viable alternative. About 10cm thick at the spine, it takes 240 disks, 4 per side each in their own scratch-proof sleeve. A thick carry handle is positioned in the centre of the spine and reinforced inside to allow it to support the weight of a filled volume, which is quite heavy - certainly a few kilos.
I have used several of these and others similar for many years and they are a working alternative to having metre upon metre of shelves. The only thing missing is an index or list of contents but it would not be beyond the realms of many to create a listing on their computer. Alternatively, there are disk cataloguing software that will do the job for you and provide excellent search capabilities, provided the numbers involves were sufficient to justify the additional costs.
I have recommended a similar syetem to others whose growing collections are beginning to take over the available space. These will save about 90% of that previously used.