A systems technician deploys a dedicated host server equipped with 64\text{ GB} of physica… — CompTIA A+ (Core 1 & Core 2)

A systems technician deploys a dedicated host server equipped with $64\text{ GB}$ of physical RAM to run three guest virtual machines (VMs): a database VM allocated $32\text{ GB}$ of RAM, an application VM allocated $16\text{ GB}$ of RAM, and a web server VM allocated $16\text{ GB}$ of RAM. The hypervisor operating system requires $4\text{ GB}$ of dedicated physical RAM overhead to manage host functions and guest memory tables. When powering on the third VM, the hypervisor produces an out-of-memory error and refuses to start the VM. Which of the following best explains why the final virtual machine failed to start?

The total requested guest vRAM ( $64\text{ GB}$ ) plus hypervisor host overhead ( $4\text{ GB}$ ) exceeds the physical RAM capacity ( $64\text{ GB}$ ) of the host system.Answer
B
Hyper-Threading was disabled in the host system BIOS/UEFI firmware, preventing the CPU from mapping virtual memory addresses across hardware thread boundaries.
C
Second Level Address Translation (SLAT) failed to automatically allocate a 50% physical RAM buffer for virtual machine paging files.
D
The hypervisor requires guest virtual machines to be provisioned in memory sizes matching exact powers of two, causing the combined $64\text{ GB}$ guest request to be rounded up to $128\text{ GB}$ .

Answer

The total requested guest vRAM (

64\text{ GB}

) plus hypervisor host overhead (

4\text{ GB}

) exceeds the physical RAM capacity (

64\text{ GB}

) of the host system.

When sizing host physical memory for virtualization, total host RAM must equal the sum of all guest vRAM allocations plus the hypervisor host OS memory overhead. Here,

32\text{ GB} + 16\text{ GB} + 16\text{ GB} = 64\text{ GB}

of guest vRAM. Adding the required

4\text{ GB}

hypervisor overhead yields a requirement of

68\text{ GB}

. Because only

64\text{ GB}

of physical RAM is installed on the host, the hypervisor lacks sufficient unreserved physical memory to start the third virtual machine.

Step-by-Step Solution

Calculate total memory required for all guest virtual machines

Database VM (

32\text{ GB}

) + Application VM (

16\text{ GB}

) + Web Server VM (

16\text{ GB}

) =

64\text{ GB}

of total guest vRAM.

Determines the base vRAM capacity required by all active guest operating systems.

Add hypervisor host overhead to guest memory demand

64\text{ GB}

guest vRAM +

4\text{ GB}

host overhead =

68\text{ GB}

total physical RAM required.

Hypervisors require dedicated host memory headroom for host kernel management, page tables, and hardware device drivers.

Compare total required RAM to installed physical RAM

68\text{ GB}

required >

64\text{ GB}

installed, resulting in a deficit of

4\text{ GB}

Without sufficient physical host memory or dynamic memory ballooning configurations, the host cannot provision the final guest VM.

Key Concept

Host RAM Allocation and Hypervisor Overhead Planning

Question

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Step-by-Step Solution

Key Concept

Common Mistakes

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