Optical discs such as Blu-ray, CD and DVD are considered as robust media for long-term storage of content, as discs are dust-resistance and water-resistance, and can withstand changes in temperature and humidity when correctly stored.
Sony and Panasonic has recently announced a new “Archival Disc” for long-term digital data storage. The new format is aimed to serve film industry and cloud data centers that handle big data. The double sided, 6 layer (3 on each side) discs can store up to 300 GB of data.
From summer 2015, Sony and Panasonic plans to start launching systems with a recording capacity of 300 GB, then further expand the capacity per disc to 500 GB and 1 TB by using High Linear Density (Intersymbol Interference Cancellation technology) for signal processing.
More details: http://www.sony.net/SonyInfo/News/Press/201403/14-0310E/