If your question is: "Can I run a CQ 5.4 and a CQ 5.5 instance independently on the same instance of operating system?", then the answer is "yes, you can".
If your question is: "Can I run a CQ 5.4 and CQ 5.5 instance and let them work together via replication", then the answer is "Technically you can do this. But you shouldn't do this". And besides this aspect you should check with Daycare support first, if this case is supported at all.
Thank you for that. We’re in process of moving from 5.4 to 5.5 and testing methodologies in dev/int/qa environments prior to release in production. Specifically, we’re hoping to come up with a procedure that will avoid any downtime for our sites. They are ecommerce-related. Any suggestions for the ‘proper procedure’ for such a switchover that would provide zero downtime or at least, minimum downtime, … would be appreciated.
Jesse Josserand |Nike CDT | O: 503-532-3179 | M: 971-300-5949
If you have multiple publisher instances, you could take half of them offline and upgrade them (and your author instance). Then, when this is finished, you bring back up your author instance and your upgraded publish instances, and then take the remaining half of your publish instances offline and upgrade them. During this part of the upgrade process, the replication agents for the offline publish instances should queue up any activations so that when they are upgraded and brought back online they will receive any activations that they missed while down. If you're working with a single publisher instance, of course, this procedure will not work for you. Nor if you have multiple publishers but have too much traffic to take 50% down. If you had, for example, 4 publish instances, you could update one at a time, but you'd be in a situation where some client requests will hit a v5.4 instance and some will hit a v5.5 instance and whether or not you can work with that is up to you to decide... but I'd heartily recommend pausing all replication agents for the duration of the upgrade if you take that route.
If you update your CQ5 version, then I would use this approach:
* Blackout period for authors during the production upgrade phase
* Upgrade 1 author and 1 publish and validate their proper functioning
* Setup the new instances in parallel to the old ones.
* Switch over from the old to the new instances
This requires that you have enough free resources to hold additional instances (which do not require CPU). If you don't have enough spare resources, it might get more complex.