ExpressCluster X 3.1 for Linux Getting Started Guide - Nec

Eliminating single point of failureDisk I/O performance in mirroring data over the network (especially writing performance)System performance during mirror resynchronization in recovery from server failure (mirrorcopy is done in the background)Time for mirror resynchronization (clustering cannot be done until mirror resynchronizationis completed)In a system with frequent data viewing and a relatively small volume of data, choosing the datamirror type for clustering is a key to increase availability.Access path to the shared diskIn a typical configuration of the shared disk type cluster system, the access path to the shared diskis shared among servers in the cluster. To take SCSI as an example, two servers and a shared diskare connected to a single SCSI bus. A failure in the access path to the shared disk can stop the entiresystem.What you can do for this is to have a redundant configuration by providing multiple access paths tothe shared disk and make them look as one path for applications. The device driver allowing such iscalled a path failover driver. Path failover drivers are often developed and released by shared diskvendors. Path failover drivers in Linux are still under development. For the time being, asdiscussed earlier, offering access paths to the shared disk by connecting a server on an arraycontroller on the shared disk basis is the way to ensure availability in Linux cluster systems.ApplicationPath FailoverDriverApplicationPath FailoverDriverFigure 1-10: Path failover driverSection I Introducing ExpressCluster25