Demonstration of Database Performance Comparison using XL-FLASH™ aiming at DRAM Replacement

The solution to this problem is to introduce SCM (Storage Class Memory) as a new layer in the memory hierarchy. SCM fills the latency and capacity gap between DRAM and flash memory. There has been active research in novel memory of SCM (Fig. 2). We have announced low latency flash memory XL-FLASH™ as SCM. The read latency of XL-FLASH™ is 5μs, which is extremely fast compared to conventional flash memory (Table I).

Table. I Feature comparison table between XL-FLASH™ and conventional flash memory

We demonstrate capability of replacing DRAM for a key-value store database using XL-FLASH™, which has lower bit cost and larger capacity than DRAM. There are two important factors when designing key-value store database for XL-FLASH™. 1) An efficient data transfer interface. 2) Data placement optimized for flash based SCM.
We have developed an interface that reduces the command overhead of the NVM Express™ protocol that is commonly used in high-performance SSDs for an efficient data transfer interface, and we have created a prototype of database that allocates infrequently accessed data to XL-FLASH™.
In order to evaluate the possibility of DRAM replacement using XL-FLASH™, we have developed XL-FLASH™ demo drive (Fig. 3), and demonstrated the evaluation result that the database using DRAM and the database using XL-FLASH™ have equivalent performance in read access-dominated situation (Fig. 4). This result shows that XL-FLASH™ has the potential to solve the problems of computing systems for database applications toward data explosion era.