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iSCSI Cluster
Overview -
A PowerEdge iSCSI Cluster is an integrated system of components, including PowerEdge servers, iSCSI Initiator, Dell | EMC® iSCSI storage system(s), a cluster interconnect, and Microsoft's failover cluster software. Microsoft® Windows® 2003 Enterprise Edition Cluster Service implements two to eight node failover clustering that delivers high availability for applications and services. Optional features of a PowerEdge Cluster include advanced cluster management software, Dell OpenManageTM software, installation services, consulting services, and proof-of-concept testing.
PowerEdge iSCSI Cluster uses the existing Ethernet technology to provide a wider coverage between the PowerEdge servers, Dell | EMC® iSCSI storage system and clients. It employs easily available and inexpensive Ethernet components to provide multiple data paths and redundancy.
Active/Active and Active/Passive Configurations
Microsoft Cluster Service (MSCS) and all PowerEdge iSCSI Clusters support both active/active and active/passive cluster configurations. The term active/active refers to a cluster with at least one virtual server running on each node. For example, in a 2-node cluster configuration, when an application is running on Node 1, Node 2 does not need to remain idle waiting for Node 1 to fail. Node 2 can run its own cluster-aware applications (or another instance of the same application) while providing failover capabilities for resources on Node 1. Node 1 in turn can provide failover capabilities for resources on Node 2. An active/active cluster node must be sized appropriately to handle the load of both nodes (in the event of a failover).
The term active/passive refers to failover cluster configurations in which one or more cluster nodes is actively processing requests for cluster applications while at least one cluster node simply waits for an active node to fail. An active/passive configuration is more costly in terms of price/performance because one or more servers remain idle most of the time. It is appropriate for business-critical systems since the application can use the full power of another server in case of a failure.
Direct Attach
A direct-attached PowerEdge iSCSI Cluster configuration includes the two cluster nodes and a single storage system. In direct-attached configurations, the storage processor(s) on the Dell | EMC iSCSI storage system are connected directly to iSCSI Initiator controlled adapters in the cluster nodes. (see Figure 1).
Each clustered server has access to the shared storage system. In a direct-attached configuration with dual storage processors, the path failover software running on each node monitors the paths to the storage system and can reroute traffic in the event of a failure in the iSCSI Initiator controlled adapter, cable system, or storage processor.
Figure 1
Switch-Attach
A PowerEdge iSCSI Cluster can be integrated into an iSCSI storage network using Ethernet/IP switches. Switch-attached clusters are superior to direct-attached clusters in configuration, flexibility, and expandability. They provide secure data communication over an existing IP infrastructure with minimized interoperability barriers. Switch-attached configurations require a redundant Ethernet switch fabric.
If greater storage capacity is desired for the cluster, a Switch-attached cluster configuration can be connected to multiple iSCSI storage systems through an IP network (see Figure 2 below).
Figure 2
Cluster consolidation
Cluster consolidation is an extension of a Switch-attached cluster configuration. For an iSCSI network, cluster consolidation is commonly defined as the ability to allow multiple iSCSI clusters and stand-alone iSCSI servers to access a portion of the storage capacity offered by one or more storage systems (see Figure 3).
In a cluster consolidation, EMC's Navisphere® Access Logix software performs LUN mapping and masking to partition the storage system and assign each data volume to specific server(s) attached to the iSCSI network. The Navisphere Access Logix software gives servers explicit ownership of a data volume located within the common enclosure. For example, if two clusters are sharing a storage system that has four available LUNs (or volumes of data), Cluster 1 can be assigned LUN 0 and 1, and Cluster 2 can be assigned LUN 2 and 3. The LUN masking software prevents each server or cluster from discovering or accessing storage owned by other server or cluster nodes.
Figure 3
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A PowerEdge iSCSI Cluster is an integrated system of components, including PowerEdge servers, iSCSI Initiator, Dell | EMC® iSCSI storage system(s), a cluster interconnect, and Microsoft's failover cluster software. Microsoft® Windows® 2003 Enterprise Edition Cluster Service implements two to eight node failover clustering that delivers high availability for applications and services. Optional features of a PowerEdge Cluster include advanced cluster management software, Dell OpenManageTM software, installation services, consulting services, and proof-of-concept testing.
PowerEdge iSCSI Cluster uses the existing Ethernet technology to provide a wider coverage between the PowerEdge servers, Dell | EMC® iSCSI storage system and clients. It employs easily available and inexpensive Ethernet components to provide multiple data paths and redundancy.
Active/Active and Active/Passive Configurations
Microsoft Cluster Service (MSCS) and all PowerEdge iSCSI Clusters support both active/active and active/passive cluster configurations. The term active/active refers to a cluster with at least one virtual server running on each node. For example, in a 2-node cluster configuration, when an application is running on Node 1, Node 2 does not need to remain idle waiting for Node 1 to fail. Node 2 can run its own cluster-aware applications (or another instance of the same application) while providing failover capabilities for resources on Node 1. Node 1 in turn can provide failover capabilities for resources on Node 2. An active/active cluster node must be sized appropriately to handle the load of both nodes (in the event of a failover).
The term active/passive refers to failover cluster configurations in which one or more cluster nodes is actively processing requests for cluster applications while at least one cluster node simply waits for an active node to fail. An active/passive configuration is more costly in terms of price/performance because one or more servers remain idle most of the time. It is appropriate for business-critical systems since the application can use the full power of another server in case of a failure.
Direct Attach
A direct-attached PowerEdge iSCSI Cluster configuration includes the two cluster nodes and a single storage system. In direct-attached configurations, the storage processor(s) on the Dell | EMC iSCSI storage system are connected directly to iSCSI Initiator controlled adapters in the cluster nodes. (see Figure 1).
Each clustered server has access to the shared storage system. In a direct-attached configuration with dual storage processors, the path failover software running on each node monitors the paths to the storage system and can reroute traffic in the event of a failure in the iSCSI Initiator controlled adapter, cable system, or storage processor.
Figure 1
Switch-Attach
A PowerEdge iSCSI Cluster can be integrated into an iSCSI storage network using Ethernet/IP switches. Switch-attached clusters are superior to direct-attached clusters in configuration, flexibility, and expandability. They provide secure data communication over an existing IP infrastructure with minimized interoperability barriers. Switch-attached configurations require a redundant Ethernet switch fabric.
If greater storage capacity is desired for the cluster, a Switch-attached cluster configuration can be connected to multiple iSCSI storage systems through an IP network (see Figure 2 below).
Figure 2
Cluster consolidation
Cluster consolidation is an extension of a Switch-attached cluster configuration. For an iSCSI network, cluster consolidation is commonly defined as the ability to allow multiple iSCSI clusters and stand-alone iSCSI servers to access a portion of the storage capacity offered by one or more storage systems (see Figure 3).
In a cluster consolidation, EMC's Navisphere® Access Logix software performs LUN mapping and masking to partition the storage system and assign each data volume to specific server(s) attached to the iSCSI network. The Navisphere Access Logix software gives servers explicit ownership of a data volume located within the common enclosure. For example, if two clusters are sharing a storage system that has four available LUNs (or volumes of data), Cluster 1 can be assigned LUN 0 and 1, and Cluster 2 can be assigned LUN 2 and 3. The LUN masking software prevents each server or cluster from discovering or accessing storage owned by other server or cluster nodes.
Figure 3
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Latest page update: made by Bryant_Vo
, May 24 2007, 10:47 AM EDT
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