Distributing system services among management hosts

Configure balanced slot allocation to distribute system services evenly among management hosts. This configuration provides benefits in terms of performance and service recovery for your management hosts.

About this task

System services are, by default, started on one management host until all the CPU slots on that host are used; then another host is selected and services are started on that one until all the CPU slots on that host are used, and so on. This stacked allocation may cause some management hosts to be overloaded while other hosts remain idle.

You can, however, change this configuration, enabling system services to be evenly distributed on management hosts. You do this by changing the slot allocation for the ManagementHosts resource group to use the Balanced policy.

When slot allocation is balanced, hosts are selected according to the number of free CPU slots on the host. Because the number of free CPU slots on a host decreases with each allocation, the same host is not selected again unless it has the highest number of free CPU slots.

Procedure

  1. Change the slot allocation for your management hosts:
    1. From the cluster management console Dashboard, select Resources > Resource Planning (Slot) > Resource Plan.
    2. Select the ManagementHosts resource group.

      You are prompted that the ManagementHost resource group is for reserved use only.

    3. Click OK.
    4. Click Slot allocation policy and select Balanced: Use free slots from the host with the highest number of free slots.

      An information message appears that the balanced slot allocation policy will not affect any system services that have already been started. Only system services that are started from this moment on will be allocated using balanced slot allocation.

    5. Click OK.
  2. Apply the balanced slot allocation policy to current allocations:

    When you change the slot allocation policy, the new policy applies only to allocations requests made after the policy was changed. In some cases, you may want to apply the policy immediately so that system services are redistributed equally among management hosts. You can do this by stopping and restarting the system services. Note that restarting services affects cluster operations.

    The following table lists the default services and the effect restarting each service has on your cluster:
    Table 1. Restarting default services
    Default services Effect of restarting the service
    ServiceDirector Services cannot be registered with Service Director.
    WEBGUI The cluster management console is temporarily unavailable. Users who are currently connected to the cluster management console will need to log on again.
    WebServiceGateway New clients cannot connect to the cluster through the Web Services API.
    RS Package deployment is not available.
    purger Data is not purged from the database.
    plc Data is pending for collection.
    derbydb Data cannot be stored in the Derby database.
    REST The REST API is temporarily unavailable.
    SD New client applications cannot connect to IBM® Spectrum Symphony. SOAM commands cannot be run.
    1. Log on to the egosh command line.
    1. View how services are allocated among management hosts and make a note of which services you want to redistribute among management hosts. 
      egosh service list -l
    2. Restart system services so that slots are allocated from management hosts according to the new allocation policy.
      To restart all system services in the cluster:
      egosh service stop all
egosh service start all
      To restart each service, replace service_name with the name of the service:
      egosh service stop service_name
egosh service start service_name
      For example, to restart the WEBGUI:
      egosh service stop WEBGUI
egosh service start WEBGUI
    3. View redistribution of services among management hosts. 
      egosh service list
    4. For each application in your cluster, disable and enable it to restart the session manager.
      Important: When you disable an application, workload is terminated.
      soamcontrol app disable myapp -s
soamcontrol app enable myapp
    5. View redistribution of session managers among management hosts. 
      soamview app