The answer is a physical mode RDM (Raw Device Mapping). This is the correct choice because physical RDM passes SCSI commands directly from the virtual machine to the SAN LUN, fully supporting SCSI-3 persistent reservations, which are required by clustered applications like Microsoft SQL Server Failover Cluster Instances or Windows Server Failover Clusters. In contrast, virtual compatibility mode (virtual RDM) intercepts SCSI commands and does not support persistent reservations, while a standard VMDK on VMFS lacks the necessary low-level SCSI command passthrough. On the VMware Certified Professional Data Center Virtualization VCP-DCV exam, this question tests your understanding of storage protocol requirements for clustering, often appearing as a trap where candidates mistakenly choose virtual RDM or VMDK. A reliable memory tip is to associate "physical" with "persistent" — both start with "P" — reminding you that physical RDM is the only option that preserves SCSI-3 reservation commands for shared LUN access across hosts.
VCP-DCV Configure and Manage vSphere Storage Practice Question
This VCP-DCV practice question tests your understanding of configure and manage vsphere storage. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An administrator needs to attach a SAN LUN to a VM for a clustered application that requires SCSI-3 persistent reservations. The VM will run on two hosts in a cluster. Which storage option should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a physical mode RDM (Raw Device Mapping).
Physical RDM (Raw Device Mapping) supports SCSI-3 persistent reservations and allows sharing the LUN between VMs in a cluster. Virtual compatibility mode (virtual RDM) does not support persistent reservations. Option A is incorrect because VMDK on VMFS does not support persistent reservations. Option B is incorrect because virtual RDM does not support it.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Create a virtual mode RDM (Raw Device Mapping).
Why it's wrong here
Incorrect: Virtual mode RDM does not support SCSI-3 persistent reservations.
Static NAT maps one inside address to one outside address.
✗
Create a thick-provisioned eager zeroed VMDK on VMFS.
Why it's wrong here
Incorrect: VMDK files do not support SCSI-3 persistent reservations.
✗
Create a VVol representing the LUN.
Why it's wrong here
Incorrect: VVols are abstracted and do not provide raw LUN mapping.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related VCP-DCV NAT questions on configuration and troubleshooting.
Configure and Manage vSphere Storage — This question tests Configure and Manage vSphere Storage — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Create a physical mode RDM (Raw Device Mapping). — Physical RDM (Raw Device Mapping) supports SCSI-3 persistent reservations and allows sharing the LUN between VMs in a cluster. Virtual compatibility mode (virtual RDM) does not support persistent reservations. Option A is incorrect because VMDK on VMFS does not support persistent reservations. Option B is incorrect because virtual RDM does not support it.
What should I do if I get this VCP-DCV question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related VCP-DCV NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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