Memory controller

Computer hardware

CAS latency

Ecology

Biology

Memory management

Exploit

Interleaved memory

Embedded system

Computer security

Dram

Operating system

Universal memory

Parallel computing

Computer science

Semiconductor memory

Cache

Host (biology)

PLoS ONE

Solid-state drives (SSDs) that do not have internal dynamic random-access memory (DRAM) are being widely spread for client SSD and embedded SSD markets in recent years because they are cheap and consume less power. Obviously, their performance is lower than conventional SSDs because they cannot exploit advantages of DRAM in the controller. However, this problem can be alleviated by using host memory buffer (HMB) feature of Non-Volatile Memory Express (NVMe), which allows SSDs to utilize the DRAM of host. In this paper, we show that commercial DRAM-less SSDs clearly exhibit worse I/O performance than SSDs with internal DRAM, but this can be improved by using the HMB feature. We also present methods that reveal how the host memory buffer is used in commercial DRAM-less SSDs to improve I/O performance. Through extensive experiments, we conclude that DRAM-less SSDs evaluated in this study mainly exploit the host memory buffer as an address mapping table cache rather than a read cache or write buffer to improve I/O performance.

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