I do not share the view that the unification of RAM and disk requires or entails linear regions of memory. In fact, the unification reduces the question of «do I have a contiguous block of size N to do X» to a mere «do I have enough memory to do X?», commits and rollbacks inclusive.

The issue of durability, however, remains a valid concern in either scenario, but the responsibility to ensure durability is delegated to the hardware.

Futhermore, commits and rollbacks are not sensitive to the memory linearity anyway; they are sensitive to durability of the operation, and they may be sensitive to the latency, although it is not a frequently occurring constraint. In the absence of a physical disk, commits/rollbacks can be implemented using the software transactional memory (STM) entirely in RAM and today – see the relevant Haskell library and the white paper on STM.

Lastly, when everything is an object in the system, the way the objects communicate with each other also changes from the traditional model of memory sharing to message passing, transactional outboxes, and similar, where the objects encapsulate the internal state without allowing other objects to access it – courtesy of the object-oriented address space protection, which is what the conversation initially started from.