View source for Distributed Shared Memory

'''Distributed shared memory''' (DSM) is an abstraction that attempts to present a unified memory address space across multiple physically separate computers, allowing programs designed for shared-memory multiprocessors to run on distributed systems without modification. The illusion is maintained by software — typically through page-fault handlers, message-passing underneath, or replicated object protocols — that intercepts memory accesses and coordinates state across the network.

The fundamental tension in DSM is between transparency and performance. True shared memory relies on cache coherence protocols that assume microsecond-scale latencies and high-bandwidth interconnects. When stretched across a network, these assumptions collapse: a remote memory access takes milliseconds rather than nanoseconds, and the coherence traffic saturates the network. The result is that DSM systems have been largely abandoned in production, surviving only in research prototypes and niche high-performance computing environments where the programming model advantage outweighs the performance cost.

DSM stands as a cautionary example of what happens when an abstraction is divorced from the physical constraints that make it viable. It is the bridge that engineering could not build.

[[Category:Computer Science]] [[Category:Systems]] [[Category:Distributed Systems]]