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Persistent memory

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This article is about computer science concept. For other uses, see The Persistence of Memory (disambiguation).

In computer science, persistent memory is any method or apparatus for efficiently storing data structures such that they can continue to be accessed using memory instructions or memory APIs even after the end of the process that created or last modified them.[1]

Often confused with non-volatile random-access memory (NVRAM), persistent memory is instead more closely linked to the concept of persistence in its emphasis on program state that exists outside the fault zone of the process that created it.

Efficient, memory-like access is the defining characteristic of persistent memory. It can be provided using microprocessor memory instructions, such as load and store. It can also be provided using APIs that implement remote direct memory access verbs, such as RDMA read and RDMA write. Other low-latency methods that allow byte-grain access to data also qualify.

Persistent memory capabilities extend beyond non-volatility of stored bits. For instance, the loss of key metadata, such as page table entries or other constructs that translate virtual addresses to physical addresses, may render durable bits non-persistent. In this respect, persistent memory resembles more abstract forms of computer storage, such as file systems. In fact, almost all existing persistent memory technologies implement at least a basic file system that can be used for associating names or identifiers with stored extents, and at a minimum provide file system methods that can be used for naming and allocating such extents.

See also

  • Persistent data, mainly to understand the kind of data that should be stored in persistent memory as opposed to the Working set. As of 2016, with modern nonvolatile memories getting fast enough and cheap enough (e.g., 3D_XPoint) to eliminate this distinction strictly on a cost basis, one could still distinguish between working set and persistent data, but mainly from the perspective of the quality of information retained in the long term.
  • Persistent data structures, such as linked lists and trees, both frequently used in database index design, that support safe modification of persistent state
  • Persistence (computer science), the characteristic of data that outlives the execution of the program that created it

References

  1. ^ Satish M. Thatte. 1986. Persistent memory: a storage architecture for object-oriented database systems. In Proceedings on the 1986 international workshop on Object-oriented database systems (OODS '86). IEEE Computer Society Press, Los Alamitos, CA, USA, 148-159.
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