Patching of the Skype for business front end pool is critical as well as very risky. Certain steps needs to be followed for SFB pool patching. Below are the steps to follow during patching of SFB servers.
Verify the replica status of the pool running below
Get-CsPoolFabricState -PoolFqdn <PoolFQDN>
If the result shows any missing replicas fix/recover the same using below command
Reset-CsPoolRegistrarState -ResetType QuorumLossRecovery
If you are applying Cumulative Updates to SFB servers verify the upgrade readiness state before applying CU
If the result is not ready wait till the readiness of the upgrade domain. Apply the cumulative updates based on the Upgrade domain
Once both the commands are verified failover the computer which is going to be patched first.
Invoke-CsComputerFailOver -ComputerName <Front End Server to be patched>
Apply the patches to the server
Run the below command once the server returned back after patching.
Invoke-CsComputerFailBack -ComputerName <Front End Server patched>
Follow the above steps on each Front End servers one by one.