Virtual machine clustering is an infrastructure configuration, where two systems and applications act as a single, logical unit. There is no direct connection to VMware vSphere. Clustering must be supported by the underlying operating system or the application itself.
In general, both systems must have simultaneous write access to the storage device so both can act as a primary or standby instance.
Mission-critical systems such as production databases are usually clustered, so in any situation, you have at least one instance available. For this reason, you can't use VMware HA technology because, as we have already explained, the VM restarts during the HA failover, resulting in application downtime. You can, in theory, use FT, but there will be limitations as well. In the case of FT, there are two significant disadvantages—performance degradation...
