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Extended Performance And Enhanced Reliability Technology (XPERT)

Micron P400m SSD Review: High Endurance MLC Is Here To Stay
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Any time we talk about a product built using components and technologies from one vendor, we have to consider the advantages of vertical integration. SSD vendors that manufacture the NAND in their drives have an inherent advantage over the companies that buy their memory. This can show up in pricing, in performance, or in reliability. In each case, though, it's only possible to extract those benefits through comprehensive testing.

With its P400m, Micron is hoping to differentiate itself from the competition through a set of enhancements designed to extend the SSD's life and guarantee the reliability of stored data. Some of the comprising features have shown up previously, while others are completely new. Micron calls this collection of storage architecture features XPERT, for eXtended Performance and Enhanced Reliability Technology.

The first feature in XPERT, dubbed Adaptive Read Management/Optimized Read (ARM/OR), is described by Micron as: a dual-faceted data management technique with both proactive and inline protection. In proactive mode, ARM/OR ensures that data stored on the SSD is immediately available by sampling the stored data and dynamically tuning the NAND device in the background. This tuning, based on Micron-specified thresholds, is completely transparent with no effect on drive or system performance. ARM/OR inline mode provides additional protection by making fast and precise foreground tuning when the host reads data from the XPERT-enabled SSD. 

Memory cells change over time, based on wear. If a controller continues to access them the same way during an SSD's life, the point at which you'll start experiencing bit errors will be sooner than if read parameters are adjusted dynamically. ARM/OR runs in the background, sampling the memory and tuning it based on thresholds defined by Micron. This management helps extend the useful life of the NAND, simultaneously allowing the company to use less expensive memory and lowering the total cost of ownership.

The next feature in XPERT is DataSAFE, which Micron says: protects user data as it moves from the host to the SSD interface, through the data path inside the SSD, into the storage media, and back. In addition, DataSAFE embeds the host logical block address (LBA) with the host data before storing both in the drive. Storing this additional information (also known as metadata) helps to ensure that XPERT-enabled SSDs return the exact data requested. In addition, DataSAFE includes error-correcting code, which protects data by adding ECC coverage to the information as it enters the DRAM on the SSD. This also ensures that data is committed to NAND without modification.

The final feature is dubbed RAIN, or Redundant Array of Independent NAND. We last saw this feature in Micron RealSSD P320h Review: A PCIe Drive Capable Of 3.2 GB/s. RAIN is most easily characterized as a RAID 5 implementation across flash channels. In the P400m, the implementation is 15+1, meaning you get 15 elements of user data and one element of parity data.

Looking at the individual components of XPERT, you can see how they all fit together. Micron is using a layered approach to data management. While each feature focuses on separate functional blocks and data paths, they all emphasize data integrity and protection.     

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