Software and hardware cluster models

A cluster is a group of two or more items that operate together to improve the overall performance, reliability, and availability of the component. The items in a cluster can be either hardware or software CIs but they must be instances of the same hardware or software class.

Clusters are modeled by using the BMC_Cluster class, which stores information about the cluster in relation to the BMC_System component.

Related topics

Managing the Common Data Model

Computer system models

The following diagram illustrates a hardware cluster model:

Logical identity of BMC_Cluster class

The Name attribute of the BMC_Cluster class identifies software and hardware clusters.

Attribute	Usage
Name	Attribute identifier that represents the cluster. The Name attribute represents all the hardware and software in the cluster.

Key attributes of BMC_Cluster class

The following attributes of the BMC_Cluster class further define software and hardware clusters:

Attribute	Description
isVirtual	Specifies whether the instance is virtual or physical. Values are NULL, No (0), or Yes (1). If you know that it is a virtual machine, use Yes. If you know that it is a physical machine, use No. If you are unsure, use NULL.
ClusterType	1- Hardware cluster 2- Software Server cluster
Interconnect	Attribute that specifies the interconnection mechanism for the cluster.
MaxNumberOfNodes	Attribute that specifies the maximum number of nodes that can participate in the cluster. If the number is unlimited, enter 0 (zero).

Name, ClusterType, and Types attributes

Name, Model, and Manufacturer attributes of the BMC_Cluster CI represent the cluster hardware or software. The ClusterType attribute specifies whether the cluster contains hardware or software items. A cluster has the following characteristics:

Failover
Performance
Distributed OS
Node Grouping
SysPlex

A cluster can have multiple characteristics, such as failover and performance.

VMware ESX clusters that are used for HA and load balancing

A VMware ESX Server cluster is a group of two or more physical ESX machines that provide resources for the Virtual Machine (VM) hosts created on this cluster. A VMware ESX cluster is used mainly for high availability and load balancing. With high availability (HA), if one of the physical machines goes down, the other physical machine starts up the virtual machines. With load balancing, if one physical machine is overloaded, then a virtual machine is moved to the other physical machine.

The following diagram shows a typical model of VMWare ESX cluster:

The modeling details of the above diagram are as follows:

A VMware cluster consisting of two physical ESX servers host-10 and host-18 is created. The cluster is modeled as a BMC_Cluster CI.
The cluster is connected to each of the ESX servers.
The ClusterType attribute of this CI is set to Software Cluster.
BMC_Component with Name=CLUSTEREDSYSTEM represents the relationship between the cluster and its items. In this case, cluster CI is the source and the ESX servers are the destinations.
Two virtual machines are provisioned on the cluster. BMC_Dependency with Name=HOSTEDLOGICALSYSTEM represents a relationship between the cluster and the virtual machines.

Recommendation

BMC recommends that you specify the type of cluster, even though the Types field is not populated as shown in this example.

Application and software clusters

Modeling clusters of software and applications provide you the flexibility to add cluster CIs at any stage of data modeling. For example, an application CI is deployed on an application system CI, and the application server CI, in turn, has several software server CIs that are running on computer system CIs. In such a case, all the software servers can be clustered. This cluster of software server CIs operates as a single unit.

To model such clustered software servers, you must have a BMC_Cluster cluster CI with all software servers as items, and a BMC_Component relationship with Name=CLUSTEREDSYSTEM represents a relationship between the items. The application system CI then connects to this BMC_Cluster CI instead of connecting to each of the individual software servers.

Similarly, a cluster CI can be introduced that represents a hardware cluster of computer systems CIs. In this type of model, the software servers are connected to this cluster CI. That cluster CI is in turn connected to computer system CIs by using a BMC_Component relationship with Name=CLUSTEREDSYSTEM.

Database clusters

Database clusters can be modeled in a similar manner as application clusters and software clusters. In a non-clustered database model, a BMC_Database CI represents the logical database. This logical database is related to a BMC_SoftwareServer CI by using a BMC_Dependency relationship. The a BMC_SoftwareServer CI represents a SoftwareServerType=DatabaseServer software instance.

However, in a clustered database model, a BMC_Cluster CI can be introduced in between BMC_Database CI and BMC_SoftwareServer CIs to represent the clustered database. The BMC_Cluster CI contains the software servers as components that together as a whole represent the database servers.

Sysplex clusters

Systems Complex (Sysplex) is a logical system running on one or more physical systems. A BMC_Cluster CI represents Sysplex. This cluster has two partitions denoting the cluster items that are related by using the BMC_Component relationship. In the following diagram, several software servers are shown running on the cluster. Each software server is modeled as a BMC_SoftwareServer CI and connected to the cluster by a BMC_Dependency relationship with Name=APPLICATIONSYSTEMCLUSTERDEPENDENCY.