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Hi.
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I'm Andy Rudoff from Intel.
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In this video, I'll explain what persistent memory is
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and why there's so much excitement around it.
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Don't forget to watch the rest of this playlist
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on persistent memory programming.
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Let's start by describing what persistent memory is.
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Sometimes called storage class memory,
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persistent memory is only recently
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available on modern hardware due to the emergence
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of new memory technologies such as Intel's 3D XPoint memory.
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These new technologies allow products
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with the attributes of both storage and memory.
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These products are persistent, like storage,
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meaning they hold their contents even across power cycles.
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And they're byte addressable, like memory,
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meaning programs can access data structures in place.
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But what really makes persistent memory stand out
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is that it's fast enough to access directly
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from the processor without stopping
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to do the Block I/O required for traditional storage.
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Performance is why there's so much
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recent excitement in the industry
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around persistent memory.
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If you compare a modern NAND-based SSD which
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plugs into the PCIe bus and communicates using MDM Express
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protocol, you can see the time it
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takes to read a block is over 80 microseconds.
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Notice how most of the time is spent accessing the media
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indicated by the blue area.
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The software stack is a small percentage
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of the overall access time.
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We could work on making the device driver faster
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and the difference would be hardly noticeable.
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The Intel Optane SSD also plugs into the PCIe bus,
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but uses 3D XPoint, so the time spent accessing
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the media shrinks way down.
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Now notice that the overhead of the software stack in the PCIe
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protocol is a significant portion of the overall latency.
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To get the most out of 3D XPoint technology,
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it now makes sense to tackle the overhead of both software
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and the interconnect.
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That's where persistent memory comes in.
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By connecting the media to the memory bus,
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the CPU can access the data directly
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without any driver or PCIe overhead.
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And since memory is accessed in 64-byte cache lines,
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the CPU reads only what it needs to read
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instead of rounding every access up
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to a block size like storage.
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You can see how low latency a 64-byte read is here,
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although I also show a 4K read for an apples-to-apples
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comparison with the SSDS.
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With persistent memory, applications
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have a new tier available for data placement.
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In addition to the memory and storage tiers,
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the persistent memory tier offers
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capacities larger than DRAM and performance significantly
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higher than storage.
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Applications can access persistent memory resident data
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structures in place like they do with traditional memory.
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This eliminates the need to page blocks of data
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back and forth between memory and storage.
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To get this low latency direct access,
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we need a software architecture that
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allows applications to connect up with ranges
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of persistent memory.
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That's the topic of the rest of this video series.
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Re-architecting your software will take some time.
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Get started right away by watching this persistent memory
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programming playlist.
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And don't forget to check out the links in the description
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below.
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[INTEL THEME MUSIC]
