The VCDX candidates advantage over the panellists.

As the candidate, you submit a VCDX application based on a project you have worked on from start to finish and in most case, lead from a technical/architectural perspective.

You therefore should have:

  • Had Initial discussions with the customer about requirements.
  • Lead or been involved in Design workshops
  • Considered design decisions
  • Documented the detailed design along with implementation & test plans etc
  • Either overseen or been actively involved with implementation

As a result of the above, you have spent many hours, potentially hundreds or thousands of hours depending on the size of the project and you will have intimate knowledge of the design & solution.

On the other hand, VCDX panellists, while they are experts in the field, have been given your application, including the design and a very limited amount of time to review and prepare for the defence.

As a result, the VCDX candidate has a HUGE advantage over the panellists!

So in a defence, who is the expert in the room on the design? The Candidate!

As a result, the candidate should be an expert in the design being presented and answering questions from the panel about the design should not be intimidating.

To all VCDX candidates, understand that you have a major advantage and go defend your design with confidence!

Example Architectural Decision – vSphere Path Selection Plugin (PSP) for IBM SVC Storage

Problem Statement

What is the most suitable multipathing policy when using IBM SVC storage?

Requirements

1. Ensure maximum performance and availability for vSphere storage
2. Ensure storage performance is as consistent as possible

Assumptions

1. IBM SVC Storage which is Active/Active
2. VAAI is supported and enabled

Constraints

1. Solution must be supported

Motivation

1. Ensure optimal performance and redundancy
2. Minimize Latency

Architectural Decision

Use vSphere Native Multipathing Plugin (NMP) and configure “VMW_PSP_RR” (Round Robin) as the path selection policy.

Set the default PSP to “VMW_PSP_RR” (Round Robin) for SATP VMW_SATP_SVC so all new LUNs automatically use Round Robin

Justification

1. Round Robin helps ensure minimum average latency to the storage by using all available paths
2. Ensure performance is not degraded for some/all virtual machines due to a single HBA or connection being heavily utilized
3. Using “VMW_PSP_ FIXED” requires the paths to be manually load balanced to avoid thrashing a single path
4. Using “VMW_PSP_MRU” or “VMW_PSP_ FIXED” may lead to incosistent performance across the LUNs due to some paths being more heavily used than others
5. There is no MPP currently supplied by IBM for SVC storage
6. Round Robin is a supported configuration (Note: Although not specifically listed in the Compatability Matrix)

Alternatives

1. Use “VMW_PSP_FIXED” (Default) – Fixed Pathing
2. Use “VMW_PSP_MRU”  – Most Recently Used
3. Use vendor supplied Multipathing Plugin

Implications

1. None

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