VMware Certified Professional - Data Center Virtualization (VCP-DCV) Practice Exam

What could explain why a virtual machine is experiencing memory ballooning but another VM on the same host is not?

1. Both VMs are configured with identical memory reservations

2. One VM has VMware Tools enabled while the other does not

3. Both VMs are powered on at the same time

4. One VM has a memory limit set while the other does not

The correct answer is: One VM has VMware Tools enabled while the other does not

The situation where a virtual machine experiences memory ballooning while another VM on the same host does not can largely be attributed to whether VMware Tools is enabled on the virtual machines. When VMware Tools is installed and running, it allows the guest operating system to communicate with the hypervisor more effectively, enabling features like ballooning. Ballooning is a memory reclamation technique used by VMware where a memory balloon driver within the VM is utilized to reclaim memory from VMs that are over-committed. If VMware Tools is not enabled on a VM, the hypervisor cannot utilize the balloon driver to reclaim memory that the VM may not be actively using. Therefore, the VM without VMware Tools would not participate in this memory management process, resulting in no ballooning occurring for that particular VM, while the other VM with VMware Tools enabled may experience memory ballooning if it is under memory pressure. In this context, the other options explain scenarios that wouldn't directly contribute to the observed behavior. Identical memory reservations do not influence ballooning, as reservations dictate how much memory is guaranteed to the VM and not how memory is reclaimed. Having both VMs powered on concurrently does not inherently cause memory ballooning. Lastly, the presence of a memory limit on one VM compared to another