If you have large Exchange organization with multiple servers and roles, you need to be careful about update. I’ve recently updated our Exchange Servers to Update Rollup 6. I want to share my experiences with update process.

First of all, you need to update roles with this order:

1. Client Access Servers
2. Hub Transport Servers
3. Mailbox Servers (DAG)

Client Access Servers:
If you have CAS Array, you don’t need to do any extra process, you can just install updates. After installation, reboot is not required but i rebooted all CAS servers to see what happens after reboot. It’s good to check services after reboot. If they are all started, then it’s successful.

Hub Transport Servers:
One important thing about update is, if you have Forefront Protection 2010 for Exchange, then you need to stop all Forefront services before update rollup. Otherwise update process will be hanged, you need to check events and if you see failed event for start of Transport Service, then you need to stop all Forefront services and start Exchange Transport Service. Update Rollup is checking Transport Service status frequently, so after service is started, update will be succeed. You can start Forefront services again. I rebooted my servers after update to see what happens after reboot.

Mailbox Server:
This one is really tricky. If you have DAG, you shouldn’t install update without locking replication.

You should follow these steps:

1. Suspend activation on the server you would like to upgrade:

Get-MailboxDatabaseCopyStatus -Server <Server> | Suspend-MailboxDatabaseCopy -ActivationOnly -Confirm:$False -SuspendComment "Install update rollup for Exchange 2010"

2. Perform server switchover to move databases to another available DAG member

3. Perform rollup update

4. Resume activation:

Get-MailboxDatabaseCopyStatus -Server <Server> | Resume-MailboxDatabaseCopy

5. You can switchover again.

You could also check this:

I hope this helps.