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Extending DRAM with Intel Memory Drive
Even though the DC P4800X is an NVMe device, Intel will begin providing a way to use it as a method of extending system memory while it develops Optane DIMMs for future systems.

This middleware, called Intel Memory Drive, serves as a hypervisor of sorts that will sit between the operating system and whatever complement of main memory and Optane devices are installed on the host system. Memory Drive will allow flexible provisioning of Optane-devices-as-storage and Optane-devices-as-memory to the system administrator. This technology requires no reprogramming of the operating system or applications. The Memory Drive and Optane suite will only work on Intel's Xeon platforms.

Optane can extend the capacity of a system's DRAM  thanks to its reliably low latency. That's because paging to an Optane SSD doesn't carry the uncertainty or nearly as much of the performance penalty of paging to NAND devices or a hard disk. To prove this point, Intel showed that GEMM, a type of workload commonly used in deep learning, can run (in a highly optimized form) at 2605 GFLOPS with 128GB of DRAM and 1.5TB of P4800X capacity installed, compared to 2322 GFLOPs with 768GB of DRAM alone installed. At $6080 for the Optane SSDs and roughly $2100 for a 128GB DDR4-2400 DIMM, the cost of crunching those large data sets could be more favorable with Optane, too. Achieving 768GB of DRAM with 128GB DDR4-2400 ECC DIMMs would require almost $13,000 of memory.

Even in less favorable workloads for Optane, extending DRAM with P4800X SSDs and Memory Drive could let companies trade some of DRAM's performance for the ability to get huge data sets much closer to the CPU than DRAM capacities currently allow. Intel says that a two-socket Xeon system provisioned with DRAM alone could reach 3TB of caching space, while a combination of DRAM, Memory Drive and Optane P4800X SSDs would allow that system to pack in as much as 24TB of memory-class space. A four-socket system would double that figure to 48TB. Based on our calculations, those figures are only possible with some combination of 1.5 TB DC P4800X drives, but even if those drives scale linearly with the 375GB drive's roughly $4-per-gigabyte cost, they could still economically boost the amount of memory-class cache close to the CPU in ways that DRAM alone can't.

All told, the performance improvements in Optane lead Intel to call the DC P4800X the industry's most responsive datacenter SSD, and we see no reason to contest the point. The 375GB DC P4800X will be available for $1520 starting today, and the drive should become more broadly available over the second half of this year. Intel will begin offering a 750GB version of the drive in the second quarter of this year, and a 1.5TB drive will follow in the second half of 2017. U.2 versions of these drives will also be available in the second quarter of this year for the 375GB version. U.2 versions of the larger-capacity drives will become available in the second half of the year.

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