Smart Write Cache

Overview

In balanced storage, to improve the read/write efficiency of HDDs, users generally use the built-in Bcache module of the Linux kernel to accelerate drive throughput. Although the acceleration effect is obvious, in scenarios where a large number of small files are written, the IOPS fluctuates greatly or even drops to zero (as shown in Figure 1), affecting user experience. As shown in Figure 2, the smart write cache feature stabilizes data streams and improves throughput.

Figure 1 IOPS of an x86 model without smart write cache

Figure 2 IOPS of a Kunpeng model with smart write cache enabled

Technical Principles

The Bcache performance is unstable because it does not have the QoS function and the cache efficiency is low. The smart write cache feature introduces bandwidth and IOPS traffic limiting measures and optimizes cache management to stabilize data streams and improve throughput.

Figure 3 Reduced IOPS fluctuation through the dual-token solution of smart write cache

Expected Results

The integration test with the Ceph cluster shows that the write performance is 1.2 times and the mixed read/write performance is 1.1 times the corresponding performance before optimization.

Parent topic: Features