In health IT, strategic tiering is the key to best flash use

Triple-level cell NAND flash storage devices wear out quickly, says one expert, but TLC devices are a good choice for Tier 2 storage and read-heavy applications.

Jeff Rowe | Feb 12, 2018 12:00 am

Flash storage is increasingly a top choice for health IT managers looking to upgrade their data storage options, but as with any serious investment it helps to recognize that flash isn’t necessarily the right choice for every storage problem.

As Brien Posey, a tech writer who was also CIO for a national chain of hospitals and healthcare facilities, recently summed it up, “TLC NAND flash memory has gained favor among IT pros because of its relatively high capacity and low price compared to other types of flash memory. But TLC is not general-purpose flash storage.”

Triple-level cell (TLC) NAND flash memory is designed to store three bits of data per cell, Posey explains. “A TLC flash device can accommodate 50% more data than a multi-level cell (MLC) device that has the same number of cells. Storing a larger amount of data in each cell reduces the cost per GB of flash storage.”

That said, Posey goes on to not that not all of TLC NAND flash memory's characteristics are positive. “Because each cell accommodates three bits of data, the cells can wear out more quickly. Increasing the number of bits that can be stored in a cell also increases the chances that the cell will be written to more frequently than it might if it could accommodate less data. Plus, TLC NAND is slower than flash storage devices that store fewer bits per cell.”

So when is TLC NAND flash storage the preferred option?

Says Posey, “In the data center, TLC storage is best suited to read-heavy workloads. NAND cell wear only occurs with write operations, so applications that read data frequently but make comparatively few writes are well-suited for use with TLC flash storage.”

TLC NAND flash memory is also suited for use as tier 2 storage, he adds. “Multi-tier storage architectures commonly use low-capacity, high-performance flash for the first storage tier and slower, higher-capacity flash for the second tier. The idea is that the system can dynamically move hot blocks to tier 1 storage and keep cool blocks on tier 2 storage. This architecture ensures that the highest-demand data is placed on the highest-performance storage media.”

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