Latency Aware Page Migration for Read Performance Optimization on Hybrid SSDs

The high-density flash memory makes it possible to store more information in a memory cell, while the drawbacks to it are degraded performance, less endurance, and wide variation of read latency. The prevalent hybrid solid state drives (SSDs) utilize a single-level cell (SLC) region as the write cache of high-density flash memory region and solve the problem of writes. However, this design did not take the read latency variation into consideration. Through evaluations on real storage device, we demonstrated the variation of read latency and presented the benefits and limitations on read performance optimization. Motivated by that, an efficient migration strategy, latency aware page migration (LAPM), is proposed. Its basic idea is to identify frequently read pages with high read latency and migrate them to the SLC region to improve the overall read performance. Experimental results show that LAPM can effectively reduce the read latency by 20% on average over the baseline while lowering the migration traffic to the device by up to 40%, compared with state-of-the-arts.