How to Disable A Real Server For Maintenance using Drain Time
To take a Real Server out of service for maintenance, navigate to Real Servers and click Disable for the Real Server that you would like to perform maintenance on. To disable more than one Real Server, select the check boxes of the Real Servers you want to disable and click Disable at the bottom left of the screen.
this will disable all instances of the real server. 
if you want to disable that real server for only certain services, you can disable the server under the virtual service
When disabling a Real Server, active connections are not dropped.
However, no new connections are sent to the Real Server.
Connections with a persistent entry are allowed to reconnect to the Real Server until the L7 Connection Drain Time expires.
The factors that determine how connections are handled when disabling a Real Server reside in the LoadMaster’s L7 Configuration.
Drain Time
System Configuration > Miscellaneous Options > L7 Configuration > L7 Connection Drain Time
L7 Connection Drain Time is a feature used to help make the administration of your Real Servers more seamless. When you disable a Real Server, L7 Connection Drain Time begins counting down from the specified time.
During this process, the LoadMaster forwards any new connections to the remaining servers in your cluster. Active connections continue relaying application data to a disabled server until that connection is terminated, or the Drain Time time has expired and the Drop at Drain Time End check box is selected.
Drop at Drain Time End
System Configuration > Miscellaneous Options > L7 Configuration > Drop at Drain Time End
When enabled, active connections are dropped from the server when the L7 Connection Drain Time expires.
By default, the Drop at Drain Time End function is disabled and the L7 Connection Drain Time is set to 300 seconds. The drain time is entered in seconds from 60 to 86400 seconds. Entering a value of 0 seconds disables the L7 Connection Drain Time.
Scenario 1:
A Real Server must be disabled for maintenance. Active connections remain until they are closed by the client or server. No new connections are sent to the Real Server:
- Ensure that Drop at Drain Time End is not enabled.
- Modify the L7 Connection Drain Time (secs) to reflect how long you would like persistent connections to be able to reconnect to the Real Server.
- Disable the Real Server.
Scenario 2:
A Real Server must be disabled for maintenance. Active connections have a set amount of time before they are dropped from the Real Server:
- Enable Drop at Drain Time End.
- Modify the L7 Connection Drain Time(secs) to reflect how long persistent connections are able to reconnect to the Real Server and how long active connections can remain before the connections are dropped and sent to another server.
- Disable the Real Server.
Scenario 3:
A Real Server must be disabled for maintenance and all connections must be dropped from it immediately:
- Enable Drop at Drain Time End.
- Modify the L7 Connection Drain Time and set it to 0.
- Disable the Real Server.
To monitor and view how many active connections remain on your Real Server, navigate to Statistics > Real Time Statistics, click Real Servers and view Active Conns.
Figure 1.3 – Real Server Active Connections
