About Storage Node decommissioning

When decommissioning a Storage Node, objects are first copied from the Storage Node being decommissioned to other Storage Nodes so that the active ILM policy continues to be satisfied. After all objects have been copied, the decommissioned Storage Node is permanently removed from the StorageGRID Webscale system.

The StorageGRID Webscale system must at all times include the minimum number of Storage Nodes required to satisfy the active ILM policy. This means maintaining ADC quorum and, if objects are erasure coded, the minimum number of Storage Nodes required by erasure coding schemes. Before decommissioning Storage Nodes, determine the minimum number that are required to satisfy the active ILM policy. It may be that you must first add a new Storage Node before decommissioning one.

The following are restrictions to the Storage Node decommissioning process:
Note: Storage Node decommissioning may take some time (days or weeks) to complete. Plan your decommissioning accordingly. While the decommissioning process is designed in such a way as to not impact system operations, it can limit other procedures.

ADC service quorum restrictions

The StorageGRID Webscale system requires that there is always an operational quorum of Administrative Domain Controller (ADC) services. This quorum is required so that operations such as running grid tasks can be performed. Thus, Storage Nodes cannot be decommissioned if their removal affects the ADC service quorum. ADC quorum requires at least three Storage Nodes at each data center site, or a simple majority ((0.5 x Storage Nodes with ADC) + 1) if there are more than three Storage Nodes at a data center site. For example, if you have six Storage Nodes with ADCs and want to decommission three Storage Nodes, you must complete two decommissioning procedures. Because the system requires a minimum of four Storage Nodes (0.5 x 6) + 1, you can only decommission two Storage Nodes in the first decommissioning procedure. You must run a second decommissioning procedure to decommission the third Storage Node. If decommissioning will result in a loss of quorum, you need to add a replacement Storage Node hosting an ADC service prior to decommissioning the existing Storage Node.