Providing persistence for sensor streams with light neighbor WAL

Sensor database systems need to provide both freshness of data and persistence to the incoming sensor streams. To provide persistence, a disk based logging method has been widely used, however it is not applicable for sensor streams because of its tardiness. In this paper, we propose the light neighbor write ahead logging protocol(L-WAL) for sensor streams. The L-WAL is a refinement of the neighbor-WAL (N-WAL). The L-WAL needs two network interfaces and applies a relaxed protocol rather than a two phase commit protocol. Since the relaxed protocol weakens the guarantee of logging successes, we have incorporated a repair system and checker system to enhance the guarantee. The result of experiments shows that the L-WAL is about 2.13 times faster than the N-WAL when the number of concurrent sensor streams is 250 and the L-WAL can enhance the persistence of data almost for free, while the N-WAL needs to pay high cost.