Types of upgrade
SDL enables multiple ways to upgrade your product, including staged and rolling upgrades.
All-at-once
Although not common, you can of course environments and software components all at one time. This type of upgrade involves greater risk and downtime.
Staged upgrade
A staged upgrade is where you upgrade the different parts of your infrastructure at different times. In a staged upgrade, you must upgrade Content Manager environment before you upgrade your Content Delivery environments. After that, you can upgrade the individual Content Delivery environments in any order you wish. Most organizations upgrade the product using a staged upgrade.
Rolling upgrade
In a rolling upgrade, you separately upgrade the parts of an environment so that you can minimize system downtime and guarantee that that upgraded parts of an environment continue to work while you continue with the upgrade. In particular, the rolling upgrade means first upgrading the shared database and then upgrading the various server components. A rolling upgrade can be especially helpful in a scaled-out setup.
Upgrade with a move to a new environment
There may be times when the hardware on which you are running an existing software component is unsuitable for use with the upgraded Tridion software. It could be that the hardware is not supported by the new version or is perhaps generally outdated. Whatever the reason, you will want to upgrade your hardware in addition to your software.
If your upgrade of Tridion Sites involves new hardware or an operating system upgrade, you are technically doing a fresh install of the software on the new hardware; however, functionally, you are still doing an upgrade. In most cases, there are customizations, configurations, and other settings from the old environment that need to be moved to the new machine. Always follow the process outlined in this section and the upgrade instructions, not the installation instructions.
Upgrade and move to the Cloud
The upgrading documentation describes how to upgrade each part of your SDL Tridion Sites system to the SDL Tridion Sites 9.1 on-premises release of SDL Tridion Sites. Alternatively, you can also choose to move some or all parts of your on-premises SDL Tridion Sites instance into the Cloud. Moving into the Cloud is a big decision with multiple decision points, but it also offers considerable benefits.
To discuss this option, contact your contact your SDL representative.