Described herein are method and apparatus for servicing software components of nodes of a cluster storage system. During data-access sessions with clients, client IDs and file handles for accessing files are produced and stored to clients and stored (as session data) to each node. A serviced node is taken offline, whereby network connections to clients are disconnected. Each disconnected client is configured to retain its client ID and file handles and attempt reconnections. Session data of the serviced node is made available to a partner node (by transferring session data to the partner node). After clients have reconnected to the partner node, the clients may use the retained client IDs and file handles to continue a data-access session with the partner node since the partner node has access to the session data of the serviced node and thus will recognize and accept the retained client ID and file handles.