What must be enabled in SMB to ensure nondisruptive upgrades?

SMB Continuous Availability (CA) is a feature of the SMB 3.x protocol specifically designed to maintain client sessions during disruptive events, such as a node reboot during a software upgrade. When enabled on a PowerScale SMB share, it allows for transparent client failover. If a node goes offline, active SMB sessions are seamlessly transferred to another healthy node in the cluster without interrupting the user or application. This is essential for achieving nondisruptive upgrades (NDUs) for Windows clients.

A. SMB multichannel provides increased throughput and network path resiliency but does not handle transparent session failover during a node reboot.
B. SMB encryption is a security feature for data in transit and has no role in high availability or nondisruptive operations.
C. SMB direct (RDMA) is a performance-enhancing feature that reduces CPU overhead; it does not provide session persistence during failover.

1. Dell PowerScale: OneFS SMB Best Practices, White Paper, August 2023, Page 11: "Continuous Availability allows for stateful SMB clients to failover non-disruptively... This feature is critical for Hyper-V and SQL Server over SMB."

2. PowerScale OneFS 9.5.0.0 Web Administration Guide, "SMB shares," Page 138: "Enable continuous availability: Provides nondisruptive failover of client connections."