Add On: This procedure also works for the new Juniper MAG appliances. But keep in mind during the upgrade of the second host (and also the first): BE PATIENT!!
A Juniper SA cluster can be configured as active/active or active/standby cluster. An active/active cluster uses an external load balancer or DNS round-robin to enable load-sharing across multiple appliances. Today I had to upgrade an active/standby cluster and found an KB article on the Juniper website (restricted access) about the preferred upgrade method.
Juniper uses the following steps to upgrade a cluster:
The following notes are mentioned by Juniper:
I followed the steps mentioned above and the upgrade of the IVE cluster went smoothly. I disabled the passive node and upgraded the firmware with the new package. After the upgrade (and a reboot) the passive node was reachable in standalone mode. Next I logged in to the active IVE and enabled the passive node back into the cluster. When you hit Enable you receive the warning message that the configuration of the new cluster node will be erased and overwritten with the configuration of the active node. Just choose Yes.
After enabling the passive node, you will loose your web session with the active node. The VIP address is taken over by the new node in the cluster and the “old active” node starts updating automatically. This is a little tricky, because you don’t notice anything from the update process taken place. Just have patience and ping the node to check when it is online again. When the node is back online, login to the IVE and check the Cluster Status. Both IVE are now updated and members of the cluster. You could decide to do a manual Fail-Over IP to the “old active” node so everything is back to the original state before the upgrade.