HMB in DRAM-less NVMe SSDs: Their usage and effects on performance

Area of Science:

• Computer Engineering
• Storage Technology
• Performance Optimization

Background:

• DRAM-less Solid-State Drives (SSDs) are increasingly popular in client and embedded markets due to lower cost and power consumption.
• These drives traditionally exhibit lower performance compared to SSDs with internal DRAM due to the absence of a dedicated memory cache.
• The Non-Volatile Memory Express (NVMe) protocol introduced the Host Memory Buffer (HMB) feature to mitigate this performance gap.

Purpose of the Study:

• To evaluate the performance impact of the HMB feature on commercial DRAM-less SSDs.
• To investigate and reveal the specific mechanisms by which HMB improves I/O performance in these devices.
• To compare the effectiveness of HMB against traditional DRAM caching strategies.

Main Methods:

• Performance benchmarking of commercial DRAM-less SSDs with and without HMB enabled.
• Comparative analysis against SSDs equipped with internal DRAM.
• Experimental methods designed to identify the functional role of the host memory buffer (e.g., read cache, write buffer, address mapping table cache).

Main Results:

• Commercial DRAM-less SSDs demonstrate significantly lower I/O performance than SSDs with internal DRAM.
• The utilization of the HMB feature demonstrably improves the I/O performance of DRAM-less SSDs.
• Experimental findings indicate that HMB is primarily employed as an address mapping table cache.

Conclusions:

• DRAM-less SSDs can achieve improved performance through the NVMe HMB feature, leveraging host system memory.
• The primary benefit of HMB in the evaluated DRAM-less SSDs stems from its function as an address mapping table cache.
• HMB serves as a cost-effective solution to enhance the performance of budget-oriented SSDs without internal DRAM.