Persistent memory, or pmem, is an exciting new storage technology that combines the durability of storage with the low access latencies and high bandwidth of DRAM. In this article, we’ll discuss the types of pmem hardware, a new programming model for pmem, and how to get access to pmem through the OS.
Persistent memory, sometimes called storage class memory, can be thought of as a cross between memory and storage. It shares a couple of properties with memory. First, it is byte addressable, meaning it can be accessed using CPU load and store instructions, as opposed to read() or write() system calls that are required for accessing traditional block-based storage. Second, pmem has the same order of magnitude performance as DRAM, meaning it has very low access latencies (measured in the tens to hundreds of nanoseconds). In addition to these beneficial memory-like properties, contents of persistent memory are preserved when the power is off, just as with storage. Taken together, these characteristics make persistent memory unique in the storage world.
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