Overview: Clustering ExtremeZ-IP 4.1

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Microsoft Cluster Servers are specially linked servers running the Microsoft Cluster Service (MSCS). If one server fails or is taken offline, other server(s) in the cluster will immediately take over the failed server’s operations. The primary purpose of clustering is to provide fast failover and quick restart of the application services provided by the failed server node. This configuration delivers the benefit of high availability for applications running on the cluster. Resources running on multiple servers appear to connected clients as a single system, referred to as a “virtual server.” When a successful failover occurs because of a problem, the connected user usually cannot tell that there was actually a brief interruption in service.


ExtremeZ-IP 4.1 Cluster Improvements

The primary change between ExtremeZ-IP 4.0 and 4.1 is that the difference between Active/Passive versus Active/Active versions of ExtremeZ-IP was eliminated. By default when you install ExtremeZ-IP 4.1 it will create a default single service allowing it to act as an Active/Passive configuration; however, at any time you can create additional Virtual Servers and it will become an Active/Active solution. Definitions of Active/Active, Virtual Server and other cluster related terms can be found below. If you are interested in finding more about clustering on ExtremeZ-IP 5.0 please refer to the ExtremeZ-IP Manual that was installed with the service.

About Microsoft Cluster Service

MSCS uses the following terms to describe the component parts of a cluster configuration. It is important not to confuse these terms as your proceed with installing ExtremeZ-IP.

  • Node – A single member server in a cluster.
  • Resource – A hardware or software component that runs in a cluster, such as a disk, an IP address, a network name, or an instance of ExtremeZ-IP.
  • Group – A combination of resources that are managed as a unit of failover. Groups are also known as resource groups or failover groups.
  • Dependency – A service or other resource that must be available first in order for the dependant service to start.
  • Failover – The process of moving resources or resource groups from one server to another. Failover can occur when one server experiences a failure of some sort or when you, the administrator, initiate the failover yourself. This term is equivalent to the Microsoft Cluster Administrator action of moving a cluster group to another node.
  • Quorum Resource – A disk resource containing the failover information that is shared between nodes in a cluster.
  • Heartbeat – The communication between Cluster nodes that allow for failover communication to occur.
  • Virtual Server – A virtual server is a combination of configuration information and cluster resources, such as an IP address, network name and an application resource.

An ExtremeZ-IP virtual server is defined by its unique IP address, Physical disk(s) and ExtremeZ-IP service. In this document, you will see the abbreviation “EVS,” meaning “ExtremeZ-IP Virtual Server.

  • Active/Active – This describes a configuration where all nodes are active ExtremeZ-IP file servers running in production.
  • Active/Passive – This describes a configuration where one node is active in production and the other nodes sit idle until a failover occurs.
  • Shared Storage – This refers to the external SCSI or fiber channel storage system. Shared storage is a requirement for multi-node clusters. Although this storage is shared, only one node can access an external storage resource at any given time.

For a more detailed explanation of ExtremeZ-IP clustering please see the Cluster Installation instructions available from the built in help for the ExtremeZ-IP Administrator, or download instructions from http://www.grouplogic.com/Knowledge/PDFUpload/Info/ExtremeZ_IP_Cluster_Setup.pdf.
If you are interested in finding more about clustering on ExtremeZ-IP 5.0 please refer to the ExtremeZ-IP Manual that was installed with the service.