Log-structured Memory for DRAM-based Storage

Traditional memory allocation mechanisms are not suitable for new DRAM-based storage systems because they use memory inefficiently, particularly under chang-ing access patterns. In contrast, a log-structured approach to memory management allows 80-90 % memory utiliza-tion while offering high performance. The RAMCloud storage system implements a unified log-structured mech-anism both for active information in memory and backup data on disk. The RAMCloud implementation of log-structured memory uses a two-level cleaning policy, which conserves disk bandwidth and improves perfor-mance up to 6x at high memory utilization. The cleaner runs concurrently with normal operations and employs multiple threads to hide most of the cost of cleaning.