pMemory

pMemory is a class of memory technologies designed to provide data persistence with low latency, blending characteristics of volatile DRAM and non-volatile storage. In many discussions, pMemory is used interchangeably with persistent memory or non-volatile memory that is byte-addressable and accessible through the system’s memory address space.

Key properties include non-volatility, byte-addressability, and latency that is significantly lower than traditional storage while typically higher than DRAM. pMemory modules can be installed alongside DRAM as DIMMs or implemented as memory-mapped non-volatile memory in server hardware. To ensure correctness across power failures, software must be written with persistence semantics using cache-line flush and fence instructions, and with crash-consistent data structures and transaction-like APIs. The programming model often requires explicit guarantees about durability boundaries, ordering, and recovery.

Architecture and software support: pMemory is accessed via the processor’s memory bus as part of the addressable memory, sometimes called memory-mapped or byte-addressable non-volatile memory. Software stacks, including libraries and runtimes, provide persistence primitives, while file systems and libraries such as PMDK (Persistent Memory Development Kit) support crash-consistent data structures and transactions. Operating systems and compilers increasingly expose instructions for cache management and persistence.

History and adoption: the term gained prominence with commercial products like Intel Optane DC Persistent Memory, which uses non-volatile memory technology to provide persistent memory capabilities in data centers. Other vendors have developed similar products. Use cases include in-memory databases with durable checkpoints, fast restart, large-scale graph analytics, and applications requiring quick recovery after failures.

Limitations and considerations: cost per gigabyte, endurance of non-volatile memory cells, and latency still exceeding DRAM, along with increased software complexity and the need for careful design of persistence guarantees and recovery procedures. pMemory remains an active area of hardware and software research and development.