Non-volatile memory technology NVDIMM

from a technical point of view, NAND Flash Flash Media Although there is a problem of the number of erase times, but with software algorithms, system-level data protection technology,NAND flash life is no longer a difficult problem, and NAND flash More advantages have become an important driving force for the technology to move forward. SSDs built with NAND Flash are rapidly replacing traditional disks, have been widely used in the Internet, and continue to penetrate into the enterprise-class market that demands data reliability.

SSDs have several very unique features compared to traditional disks. The first feature is that SSD has very good read and write performance, especially in the random read and write performance far more than the traditional disk, second,SSD has a high storage density, in the unit volume,SSD storage density is higher than the traditional disk, This year many manufacturers of 2.5 inch single-disk SSD capacity can reach 8GB, exceeding the capacity of the same volume disk; third,SSDs have better controllability in terms of data reliability,NAND Flash Storage Media life is controllable and predictable, soSSD can use the system-level application software to combine storage media life and data characteristics, so that the user's data reliability to achieve the best. On the disk, the life expectancy of the storage medium is very difficult;the SSD is a semiconductor storage, and as the market size advances,the SSD itself will cost much less than the disk, although the current SSD price is higher than the disk , but its price drops far more than the disk, the future SSD price lower than the disk is no suspense.

compared with traditional disks, SSDs are once again approaching the CPU in terms of performance , making the performance price scissors in computer architectures less and less. However, compared with DRAM memory Technology,There are some performance gaps in SSDs. when the CPU accesses the Cache(SRAM), there is an NS level of access delay; when accessing memory (DRAM), there is a 10ns Level of access latency, however, there is a 10us level of access latency when accessing the SSD. Although the MS-level access latency of the disk is reduced by an orderof magnitude, there is an order of magnitude performance gaps in SSD and DRAM access latencies. How to reduce this performance gap is an issue that the industry needs to consider.

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Judging from the current technological development, The NVDIMM just compensates for The performance gap between SSD and DRAM. the NVDIMM technology combines NAND flash,dram and supercapacitors to take advantage of the high performance ofDRAM, NAND flash High-efficiency data persistence and super-capacitor power efficiency. From a technical point of view,NVDIMM does not seem to have much innovation, the technical idea is that when the memory (DRAM) Suddenly power off the case, in the power of the super capacitor,the processing unit on the NVDIMM will The data in DRAM is migrated to NAND Flash, so that NVDIMM can guarantee the data is not lost even in the case of sudden power outage, thus achieving the non-volatile memory data. Generally speaking, a NVDIMM product form is shown, consisting of a memory card and a super capacitor of the same size as the normal RAM bar.

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This nonvolatile memory is a storage medium that the storage domain has been looking for. when NVDIMM products are not present, it is common to use UPS to protect memory data or to protect critical data in a pci-nvram manner. In the storage products,Pci-nvram use more, its product technology principle and NVDIMM similar, the difference is that Pci-nvram is based on the Pci/pcie bus, And the battery is used to protect the power-down data. Once the power is dropped,Pci-nvram can refresh the data to Flashor rely on the battery's endurance to ensure that data in the onboard DRAM is not lost. Compared with the original non-volatile memory scheme,NVDIMM discarded the bulky battery and packaged it directly into the product form of the memory strip, which has better performance and lower latency than the pci-nvram. Specific Comparisons of product technologies such as NVDIMM and NVRAM are as follows:

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NVDIMM is undoubtedly a huge impact on products such as Pci-nvram, in the foreseeable future will be in the non-volatile memory of the supremacy, its future direct competitor should be MRAM storage media. The disadvantage of NVDIMM is that the storage capacity is smaller, but with the same access performance as DRAM, it is a performance comparison between NVDIMM and SSD . NVDIMM is more than 2 times the performance of PCIe SSD in data random access performance, and the performance of NVDIMM is more than that of PCIe SSD in data access latency. Increased by more than a few times.

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because NVDIMM is a data nonvolatile feature, so it can be used as a persistent data storage layer on SSD, through the NVDIMM and SSD , at the system level to make data storage performance, data reliability, Maximum service life. As flash technology continues to move forward today, we can see the real data cache layer in NVDIMM, bulk data primary storage on SSDs, heterogeneous backup on disk, tape and future TLC Semiconductor media. Today,Intel has implemented technical support for NVDIMM on Haswell processors , and as server vendors continue to participate in the NVDIMM ecosystem, NVDIMM 's large-scale applications in storage and servers are around the corner.

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Non-volatile memory technology NVDIMM