Change of HDD Technology is expensive or difficult to use
New technology for HDD could be difficult to use (i.e. no longer random access), or inefficient for our I/O patterns. The new technolgies may also not follow a decreasing cost trend in the medium term, and could be relatively expensive.
The overall effect would be an increase in storage costs (for disk).
The future data lake model is part of a mitigation for this scenario. Focussing data storage on few large sites while delivering content to remote compute facilities would partly mitigate this. This could reduce the overall (global) cost of storage, and mitigate a cost increase.
A second mitigation is the move to the so-called "tape carousel" model, where tape is used more actively to hold the majority of active data with an on-demand and organised to stage to disk just in time for processing. This has a knock-on effect of requiring a more organised analysis model in the experiments.
The increased use of tape to mitigate disk costs, however, exxposes us to the previous risk on tape market collapse.