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Clusters Clusters Alternative to symmetric multiprocessing (SMP) Group of interconnected, whole computers working together as a unified computing resource illusion is one machine system can run on its own Clusters Separate server each computer is a separate server no shared disks need management or scheduling software data must be constantly copied among systems so each is current Clusters Standby Server with No Shared Disk P P P P High-Speed Message Link M I/O I/O I/O I/O M Clusters Shared nothing reduces communication overhead servers connected to common disks disks partitioned into volumes each volume owned by a computer if computer fails another computer gets ownership of the volume Clusters Shared Disk High-Speed Message Link P M P I/O I/O I/O I/O I/O RAID P P I/O M Clusters Shared disk multiple computers share the same disks at the same time each computer has access to all of the volumes on all of the disks Win2000 Cluster Server Formerly called Wolfpack Shared-nothing cluster Concepts Cluster Service – Software that manages cluster-specific activity Resource – Item to be managed Physical: Disk drives, Network cards Logical: Volumes, TCP/IP addresses, Applications, Databases Online – A resource is online at a node when it is providing service on that node Group – A collection of resources managed as a unit Helps manage resources, load balancing Usually a set of resources needed for a specific application Win2000 Cluster Server Components Node Manager – Maintain membership: Uses heartbeat messages to track system Database Manager – Maintain cluster configuration database (resources, groups, ownership): Uses fault-tolerant transaction software Resource Manager – Make decisions concerning resources, startup, failover Event Processor – Connect components Beowulf From NASA High Performance Computing and Communications Project, based on commodity hardware Implemented as an add-on to Linux, and each node runs a copy of Linux, with kernel extensions for global namespaces Examples of Beowulf system software: Beowulf Distributed Process Space – Allow process ID space to span machines, provide single system image, start processes on other nodes Beowulf Ethernet Channel Bonding – Combine multiple low-cost links into a single logical network Pvmsync – Provide synchronization and shared data objects in a cluster EnFuzion – Set of tools for parametric computing