New technology, new revolution, analysis of new trends in the development of SSD industry

27/09/2021

Unexpected power outages cause bricks to be the most common cause of failures in solid state drives. In order to protect the critical data in the DRAM cache, enterprise-level solid-state drives have to introduce complex protection circuits and sacrifice certain performance to periodically write back cache contents.

STT-MRAM is a kind of non-volatile memory similar to flash memory. Its speed and latency performance are closer to DRAM memory, but at the same time it retains the characteristic that data will not be lost after power failure, so it becomes an ideal replacement for DRAM cache in solid state drives. By.

In traditional solid-state hard drives, solid-state drives need to design complex data protection logic in DRAM for unexpected power failures. Utilize the energy stored in the large-capacity capacitor to safely write the data in the cache back to the flash memory when the power is off.

MRAM can partially replace DRAM cache, using its speed close to memory to safely store FTL changed parts, metadata, write cache and other parts that need to be protected, instead of the complete FTL copy and read cache that need to be fully protected still pass through traditional DRAM Chip implementation.

As for why STT-DRAM is not used to completely replace DRAM, there are still technical difficulties: the capacity of a single STT-MRAM cache is mostly between 1Gb-2Gb, and the capacity of solid-state hard disk DRAM cache is mostly matched with NAND flash memory in a ratio of 1:10. In this way, a 1TB capacity solid state drive has a cache requirement of up to 1GB. If all STT-MRAM storage is used, the manufacturing cost will be greatly increased.
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