Deleting a node from a system by using the CLI

You can use the command line interface (CLI) to remove a node from a system.

Before you begin

After the node is deleted, the other node in the I/O group enters write-through mode until another node is added back into the I/O group.

By default, the rmnode command flushes the cache on the specified node before the node is taken offline. When the system is operating in a degraded state, the system ensures that data loss does not occur as a result of deleting the only node with the cache data.

Attention:

If you are removing a single node and the remaining node in the I/O group is online, the data can be exposed to a single point of failure if the remaining node fails.
If both nodes in the I/O group are online and the volumes are already degraded before you delete the node, redundancy to the volumes is already degraded. If the force option is used, removing a node might result in loss of access to data, and data loss might occur.
Removing the last node destroys the system. Before you delete the last node in the system, ensure that you want to destroy the system.
When you delete a node, you remove all redundancy from the I/O group. As a result, new or existing failures can cause I/O errors on the hosts. The following failures can occur:
- Host configuration errors
- Zoning errors
- Multipathing software configuration errors
If you are deleting the last node in an I/O group and volumes are assigned to the I/O group, you cannot delete the node from the system if the node is online. You must back up or migrate all data that you want to save before you delete the node. If the node is offline, you can delete the node.
To take the specified node offline immediately without flushing the cache or ensuring that data loss does not occur, run the rmnode command with the force parameter. The force parameter forces continuation of the command even though any node-dependent volumes will be taken offline. Use the force parameter with caution; access to data on node-dependent volumes will be lost.
To delete a node that is in the service state and that has an associated spare node, you must specify the -deactivatespare parameter with the rmnode command.

About this task

Complete these steps to delete a node:

Procedure

If you are deleting the last node in an I/O group, determine the volumes that are still assigned to this I/O group:
1. Issue the following CLI command to request a filtered view of the volumes:
```
lsvdisk -filtervalue IO_group_name=name
```
  Where name is the name of the I/O group.
2. Issue the following CLI command to list the hosts that this volume is mapped to:
```
lsvdiskhostmap vdiskname/identification
```
  Where vdiskname/identification is the name or identification of the volume.
Note: If volumes are assigned to this I/O group that contain data that you want to continue to access, back up the data or migrate the volumes to a different (online) I/O group.
Turn off the power to the node that you intend to remove, if this node is not the last node in the clustered system. This step ensures that the multipathing device driver, such as the Subsystem Device Driver (SDD), does not rediscover the paths that are manually removed before you issue the delete node request.
Attention:
1. If you are removing the configuration node, the rmnode command causes the configuration node to move to a different node within the clustered system. This process might take a short time, typically less than a minute. The system IP address remains unchanged, but any SSH client that is attached to the configuration node must reestablish a connection.
2. If you turn on the power to the node that was removed and it is still connected to the same fabric or zone, it attempts to rejoin the system. The system causes the node to remove itself from the system and the node becomes a candidate to add to this system or another system.
3. If you are adding this node into the system, ensure that you add it to the same I/O group that it was previously a member of. Failure to do so can result in data corruption.
4. In a service situation, a node should normally be added back into a system using the original node name. As long as the partner node in the I/O group was not deleted too, this is the default name used if -name is not specified.
Before you delete the node, update the multipathing device driver configuration on the host to remove all device identifiers that are presented by the volumes that you intend to remove. If you are using the Subsystem Device Driver, the device identifiers are referred to as virtual paths (vpaths).
Attention: Failure to complete this step can result in data corruption.

See the IBM® Multipath Subsystem Device Driver User's Guide for details about how to dynamically reconfigure SDD for the host operating system.
Issue this CLI command to delete a node from the clustered system:
Attention: Before you delete the node, note the following information. The rmnode command checks for node-dependent volumes, which are not mirrored at the time that the command is run. If any node-dependent volumes are found, the command stops and returns a message. To continue removing the node despite the potential loss of data, run the rmnode command with the force parameter. Alternatively, follow these steps before you remove the node to ensure that all volumes are mirrored:
1. Run the lsdependentvdisks command.
2. For each node-dependent volume that is returned, run the lsvdisk command.
3. Ensure that each volume returns in-sync status.
```
rmnode node_name_or_identification
```
Where node_name_or_identification is the name or identification of the node.

Note: Before a node is removed, the command checks for any node-dependent volumes that would go offline. If the node that you selected to delete contains a flash drive that has dependent volumes, volumes that use the flash drives go offline and become unavailable if the node is deleted. To maintain access to volume data, mirror these volumes before you remove the node. To continue removing the node without mirroring the volumes, specify the force parameter.