Sony and Panasonic have announced a new archival disc format, which will store 300GB using double-sided, triple-layer optical discs "from summer 2015". The companies' roadmap anticipates this being increased to 500GB and then 1TB per disc. Today's Blu-ray discs — which were also developed by Sony and Panasonic — typically store 50GB or 100GB.
Sony's announcement says: "In recent times, demand for archival capabilities has increased significantly in the film industry, as well as in cloud data centres that handle big data, where advances in network services have caused data volumes to soar.
"The two companies plan to actively promote this next-generation high-capacity optical disc standard in the professional field in order to offer an effective solution for protecting valuable data into the future."
It also mentions "inter-generational compatibility between different formats, ensuring that data can continue to be read even as formats evolve", though it doesn't say if the new drives will be able to read Blu-ray. However, this is unlikely to be important to the target market.
TDK showed 1TB Blu-ray discs in 2010. However, this capacity was achieved by recording on 16 layers, exceeding the thickness allowed in the Blu-ray specification. TDK told Tech-On that "its commercialisation depends on disc manufacturers", but it doesn't appear to have had any takers.
The real competition at the moment may be Amazon Glacier. Amazon says that "customers can reliably store large or small amounts of data for as little as $0.01 per gigabyte per month, a significant savings compared to on-premises solutions".