Although the implemented solution differs from the initial demand, we are closing the request as "already available”. We have thoroughly investigated the idea to solve the redundancy issue using a Plesk cluster. Our research has proved that this solution is not in step with the times, is no longer demanded by our partners, and has its limitations. We would like to give an explanation of each point.

More than nine years ago, when the request was created, the IT world had already begun to change. Previously, partners and customers bought or rented bare-metal servers and organized them in data centers. If the servers did not have sufficient component redundancy, there was a risk that a power supply or hard drive failure would lead to service downtime. However, a synchronized failover server could save hosting from such problems. But since then, hosting infrastructure has changed significantly. These days, public clouds are everywhere, partners and customers use virtualization systems, and software runs in containers.

We interviewed our partners to make sure they still needed a high-availability (failover) cluster for Plesk. It turned out that the majority of partners already had virtualization systems in their infrastructure. To protect a server with Plesk from failures, many partners already use high-availability features provided by virtualization systems. Some partners are no longer interested in a high-availability (failover) cluster. Instead, they would like to have a high-load cluster with active/active nodes, where the load is balanced between all cluster members.

In the meantime, we tried building a Plesk cluster. It proved to be possible but with many limitations. A Plesk cluster also requires more servers and resources for deployment from partners and customers, which leads to increased infrastructure costs. The solution would be unreasonably expensive for end users. Developing a Plesk cluster further and making it suitable for production requires lots of additional investments. They will not justify themselves from the point of view of our partners, customers, end users, and Plesk itself. Should anyone decide to continue the research on how to adapt Plesk to be a part of a failover cluster, we have published our research results together with the proof of concept. If you have any feedback, we have created a topic about high availability Plesk on our forum.

Note: We recommend using a centralized database and centralized file storage (NFS) together with virtualization systems and/or cloud providers that provide high-availability functionality on the server rather than the software level. At the same time, we do not plan to continue developing any high-availability redundancy on the application level.

— AY