Memory ballooning is caused by the overcommitment of memory-intensive VMs. However, this is just indicative, which means that the presence of ballooning does not always say it's a performance problem. Ballooning is an effective way to use pRAM more efficiently, usually with no negative performance impact.

In order to maximize the ability of ESXi to recover idle memory from VMs, the balloon driver should be enabled on all VMs. The balloon driver should never be deliberately disabled on a VM. Disabling the balloon driver might cause unintended performance problems.