LND

Abstract

The expensive overhead of synchronous I/O has now become the bottleneck of increasing efficiency of data storage in transaction-based systems. This paper proposes a multi-tier storage device, the LND (Local-Network Ram- Disk) device, which uses idle memories and disks in NOW (Network of Workstations) as persistent repositories so that access latency is transformed from magnetic disk seek-and-transfer latency to the sum of network transfer latency, memory write latency, and asynchronous I/O latency. Two fast data consistency protocols based on multicast technique are also introduced to improve performance without sacrificing reliability. Experimental results show that the LND device is one order of magnitude faster than traditional disks in synchronous I/O performance. Moreover, a fault tolerant recovery algorithm is proposed to protect the system from various kinds of failures and to facilitate quick recovery from crashes.