Adding hot-spare nodes to a system

When you add nodes, you can specify up to four of them as hot-spare nodes. A hot-spare node can become online (handling I/O operations) automatically if needed. For example, if a node fails, an available hot-spare node that matches the failed node is activated automatically and moves to the Online Spare state. The hot-spare node handles I/O operations for the failed node until it comes back online. After the node returns to the system, the hot-spare node returns to the Spare state, which indicates it can be automatically swapped for other failed nodes on the system.

The loss of a node, either for unplanned reasons, such as hardware failure, or planned outages, such as upgrades, can result in loss of redundancy or degraded system performance. To reduce this possibility, a hot-spare node is kept powered on and visible on the system. A hot-spare node has active system ports, but no host I/O ports, and is not part of any I/O group. If a node fails or is upgraded, this spare node joins the system and assumes the place of the failed node, restoring redundancy. Only host connection on Fibre Channel ports that support node port virtualization (NPIV) can be used for hot-spare nodes. The hot-spare node uses the same N_Port ID Virtualization (NPIV) worldwide port names (WWPNs) for its Fibre Channel ports as the failed node, so host operations are not disrupted. The hot-spare node retains its node identifier when it was the spare. During an upgrade, the spare node is added to the system as soon as a node is removed. As each node in a system shuts down for the upgrade, it is replaced by the hot-spare node.

You can assign node pairs to specific I/O groups and then assign the extra nodes as hot-spare nodes. When a hot-spare node is added to the system, it is in Spare state, which indicates that it is not part of an I/O group. If a node in an I/O group fails, a hot-spare node automatically replaces that node and becomes a part of the I/O group. While the hot-spare node is in the I/O group, it is in the Online Spare state and returns to the Spare state when the original node rejoins the I/O group. A system can contain up to four spares at any time, which includes any hot-spare nodes that are currently online as spare nodes. Ensure that all cabling is correct to ensure that the nodes are detected by the system. If a node is not detected, review the installation information that was included with the system.

If you are running the software on generic node hardware, the spare node hardware and software level must be identical across the system.

If the nodes on the system support and are licensed to use encryption, the hot-spare node must also support and be licensed to use encryption. For enhanced stretched or HyperSwap® configurations, hot-spare nodes must be assigned to a specific site. If a node fails on a particular site, the hot-spare node that is assigned to that site is used if it is a suitable replacement. If you are using standard configuration for a stretched system, you must update to an enhanced stretched system to use hot-spare nodes. In a standard stretched configuration, hot-spare nodes can be selected from the wrong site that overloads inter-system links and causes performance issues.

Using the management GUI

If you are adding nodes to I/O groups for the first time, you can also specify hot-spare nodes by completing these steps:
  1. In the management GUI, select Monitoring > System
  2. On the System -- Overview, click Add Nodes.
  3. On the Add Node page, select the nodes to add to the I/O group and optionally select additional nodes to use as hot-spare nodes for the entire system.
If your nodes are already configured on your systems, and you want to add hot-spare nodes, you must connect the additional nodes to the system. After hot-spare nodes are configured correctly on the system, you can add the spare node to the system configuration by completing these steps:
  1. In the management GUI, select Monitoring > System.
  2. On the System -- Overview, click Add Nodes.
  3. On the Add Node page, select hot-spare node to add to the system. The system supports the maximum of four hot-spare nodes.
  4. If your system uses either stretched or HyperSwap system topology, hot-spare nodes must be designated per site.
To use hot-spare nodes on the system, ensure that the I/O group supports virtualized ports. First switches that connect hosts to the system must support N_Port ID Virtualization (NPIV). After you verify that NPIV is supported on the switch, you can ensure that the virtualized ports are enabled on the I/O group. For new systems the default status for NPIV is set to enabled; however, if you are adding a spare node to an existing system, you should verify this setting. To verify or change this value, complete these steps:
  1. In the management GUI, select Settings > System > I/O Groups.
  2. Verify that the value for the Target Port Mode attribute is set to Enabled. For new systems, the default status for NPIV is set to enabled. However, if you are adding a node to an existing system, verify this setting. If it is set to either Transitional or Disabled, it must be changed to Enabled.
  3. If the Target Port Mode is disabled, complete these steps to change it to enabled:
    1. Right-click the I/O group and select Change Target Port Mode.
    2. On the Change Target Port Mode page, select Transitional for the new state. Users cannot go directly from disabled to enabled state. The system must be in a transitional state where the I/O group contains both physical and virtual Fibre Channel ports. Click Continue.
    3. Wait approximately 2 minutes before you verify the changed state for the target ports.
    4. Verify that the new Transitional state is displayed on the I/O Groups page.
    5. Right-click the I/O group and select Change Target Port Mode.
    6. On the Change Target Port Mode page, select Enabled for the new state. Click Continue.
    7. After 2 minutes, verify that the new Enabled state is displayed on the I/O Groups page.
  4. If the Target Port Mode is already in the Transitional state, complete these steps to change the state to Enabled by completing these steps:
    1. Right-click the I/O group and select Change Target Port Mode.
    2. On the Change Target Port Mode page, select Enabled for the new state. Click Continue.
    3. Wait approximately 2 minutes before you verify that the new Enabled state is displayed on the I/O Groups page.

Using the command-line interface

To add a spare node to the system, enter the following command, where panel_name is the name of the node that is displayed in the service assistant or in the output of the lsnodecandidate command. 
addnode -panelname panel_name -spare
For enhanced stretched or HyperSwap configurations, use the following command to specify the name and site location of the spare node. 
addnode -panelname panel_name -spare -site site_id