Quick Answer
The answer is Storage I/O Control shares, which guarantee a minimum I/O share to a specific VM by allocating relative bandwidth priority on a datastore. This feature works by setting shares, limits, and reservations per VM, ensuring that a high-I/O-demand VM receives its guaranteed portion even when other VMs are consuming excessive I/O operations. On the VMware Certified Professional Data Center Virtualization VCP-DCV exam, this topic tests your ability to differentiate SIOC from Storage DRS, which balances I/O across datastores but does not enforce per-VM guarantees, and from multipathing or VM storage policies, which address path selection and provisioning, not I/O contention. A common trap is confusing SIOC shares with reservations—shares provide relative priority, while reservations guarantee absolute minimums. Memory tip: think “SIOC shares = I/O priority lane” for a single datastore, not a load-balancing highway.
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 notices that a VM with high I/O demands is experiencing performance issues because other VMs on the same datastore are consuming too many I/O operations. Which feature can be used to guarantee a minimum I/O share to this VM?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Multipathing policy
Why wrong: Multipathing policy selects paths for redundant storage, not I/O guarantees.
VM storage policy
Why wrong: VM storage policy defines provisioning requirements, not I/O performance guarantees.
Storage DRS
Why wrong: Storage DRS balances I/O load across datastores, not per-VM guarantees.
Storage I/O Control shares
SIOC uses shares to allocate relative I/O priority to VMs.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Storage I/O Control shares
Storage I/O Control (SIOC) allows setting shares, limits, and reservations to allocate I/O bandwidth per VM. Storage DRS balances I/O across datastores, not per-VM; multipathing selects paths; VM storage policies manage provisioning.
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
For each option: why learners choose it and why it is or isn't the right answer here.
Multipathing policy
Why it's wrong here
Multipathing policy selects paths for redundant storage, not I/O guarantees.
VM storage policy
Why it's wrong here
VM storage policy defines provisioning requirements, not I/O performance guarantees.
Storage DRS
Why it's wrong here
Storage DRS balances I/O load across datastores, not per-VM guarantees.
Storage I/O Control shares
Why this is correct
SIOC uses shares to allocate relative I/O priority to VMs.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
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
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.
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
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
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 — study guide chapter
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FAQ
Configure and Manage vSphere Storage — This question tests Configure and Manage vSphere Storage — Static NAT maps one inside address to one outside address..
The correct answer is: Storage I/O Control shares — Storage I/O Control (SIOC) allows setting shares, limits, and reservations to allocate I/O bandwidth per VM. Storage DRS balances I/O across datastores, not per-VM; multipathing selects paths; VM storage policies manage provisioning.
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.
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Static NAT maps one inside address to one outside address.
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Same concept, more angles
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Variation 1. An administrator is troubleshooting performance issues on a VMFS datastore hosting SQL Server VMs. Storage I/O Control (SIOC) is enabled, but the administrator notices that congestion is detected but no throttling is applied. What could be the reason?
mediumWhy A: SIOC throttles only when there is congestion and the SIOC queue depth threshold is exceeded. If the threshold is set too high, throttling may not activate. Option B is correct. Option A (disabled) would not detect congestion. Option C (wrong) about stats interval. Option D (deduplication) is irrelevant.
Last reviewed: Jun 24, 2026
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