On Using Network RAM as a non volatile Bu er

File systems and databases usually make several synchronous disk write accesses in order to make sure that the disk always has a consistent view of their data so that it can be recovered in the case of a system crash Since synchronous disk operations are slow some systems choose to employ asynchronous disk write operations at the cost of low reliability in case of a system crash all data that have not yet been written to disk are lost In this paper we describe a software based Non Volatile RAM system that provides the reliability of synchronous write operations with the performance of asynchronous write operations Our system takes a set of volatile main memories residing in independent work stations and transforms it into a non volatile memory bu er much like RAIDS do with magnetic disks It then uses this non volatile bu er as an intermediate storage space in order to acknowledge synchronous write operations before actually writing the data to magnetic disk but after writing the data to intermediate stable storage Using simulation and experimental evaluation we demonstrate the performance advan tages of our system