Inquiry on F5's Maintenance Mode Feature for Pool Members

Both "disable" and "force offline" actions may answer the requirement as they both provide some level of smoothness

1. When set to Disabled, a node or pool member continues to process persistent and active connections. It can accept new connections only if the connections belong to an existing persistence session.
2. When set to Forced Offline, a node or pool member allows existing connections to time out, but no new connections are allowed

So, for the first you need to disable the node then wait for a sufficient time to make sure there is no active nor persistent connection related to that node. Typically, you will disable a node 30 minutes to a few hours before the maintenance schedule.

For the second, you set the node to forced offline and wait a few minutes until there is no active connection to this node. Note that persistence here is immediately lost and any client who is in the persistence table but who is not actively connected will load blance to the next member.