Cluster modes and MSCS
There are two modes in which you might run a cluster system with IBM MQ on Windows: Active/Passive or Active/Active.
Note: If we are using MSCS together with the Microsoft Transaction Server (COM+), we cannot use Active/Active mode.Active/Passive mode
In Active/Passive mode, computer A has the running application on it, and computer B is backup, only being used when MSCS detects a problem.
We can use this mode with only one shared disk, but, if any application causes a failover, all the applications must be transferred as a group (because only one computer can access the shared disk at a time).
We can configure MSCS with A as the preferred computer. Then, when computer A has been repaired or replaced and is working properly again, MSCS detects this and automatically switches the application back to computer A.
If you run more than one queue manager, consider having a separate shared disk for each. Then put each queue manager in a separate group in MSCS. In this way, any queue manager can failover to the other computer without affecting the other queue managers.
Active/Active mode
In Active/Active mode, computers A and B both have running applications, and the groups on each computer are set to use the other computer as backup. If a failure is detected on computer A, MSCS transfers the state data to computer B, and reinitiates the application there. computer B then runs its own application and A's.
For this setup we need at least two shared disks. We can configure MSCS with A as the preferred computer for A's applications, and B as the preferred computer for B's applications. After failover and repair, each application automatically ends up back on its own computer.
For IBM MQ this means that you could, for example, run two queue managers, one on each of A and B, with each exploiting the full power of its own computer. After a failure on computer A, both queue managers will run on computer B. This will mean sharing the power of the one computer, with a reduced ability to process large quantities of data at speed. However, your critical applications will still be available while you find and repair the fault on A.
Parent topic: Set up IBM MQ for MSCS clustering