Most Common Errors in VCDX Defenses

This note is a companion to the recently published Most Common Errors in VCDX Applications. It focuses on mistakes frequently made specifically during the defense portion of the VCDX process.

Before and during your defense:

  1. AVOID THIS ERROR: Not knowing your own design.

    No matter what your skills are, you will not succeed in your VCDX defense unless you have an intimate knowledge of what you submitted.  Be prepared to recall every customer requirement and constraint; every design assumption; every design decision made and its rationale; and every detail of the design's implementation.  Possess a thorough understanding of the business reasons that drove the customer to request the design in the first place.

    If your design is partially or completely fictitious, you must have answers to the above questions just as a real design would.  See Pitfalls of Fictitious VCDX Designs for more details.

  2. AVOID THIS ERROR: Failing to manage your emotions and stress level.

    Officially, a VCDX defense has two possible outcomes: pass and fail. But in effect it has three:

    • Pass
    • Fail and remember the feedback you got
    • Fail and remember nothing once you walk out of the room

    Of these outcomes, only the last one is a true tragedy. Unsuccessful candidates who remember what questions the panelists asked have just gotten several hours of personal, intensive career guidance from our industry's leading experts. However, too many candidates report walking out of the room with their heads and hearts all in a whirl. Some of these candidates have in fact passed! But for all who did not, they are much less well positioned for a repeat attempt than they could be.

    First and foremost, don't thwart your body's attempts to help you manage your stress. Don't overindulge on caffeine or alcohol during the 24 hours before your defense. Do your late-night cram sessions on any night other than the one before your defense. And a medically-advised program of regular exercise, begun at least several weeks before your defense, will advance your cause in ways you may not expect.

    Second, don't let your mind become your enemy. The main way candidates undercut themselves is to start attributing motivations to the panelists' questions. Any candidate who thinks "That judge is out to get me!" or "That judge has already decided to fail me!" is wrong. See FAQ for Unsuccessful VCDX Candidates for more information. This kind of emotionally colored thinking tends to feed on itself as the defense goes on. It is doubly damaging to the candidate: he or she can't think clearly to answer questions, and his or her emotional state is not conducive to later memory.

    I regret to inform you that candidates are not allowed to take notes out of the defense room. So your memory is your sole repository of the feedback you receive there. Don't sabotage it.

  3. AVOID THIS ERROR: Failing to understand the route to success.

    VCDX is a hybrid credential.  To pass, you must meet all three of these objectives:

    • Display a certain level of design knowledge and skills.
    • Display a certain level of vSphere knowledge and skills.
    • Do both in the defined format of the defense.

    It is not possible to do so well in one of these areas that it makes up for a poor performance in the others.

    Examine the VCDX flowchart, a very simple document. Note the four decision boxes for the defense. Focus your preparation on that.  Speaking of preparation...

  4. AVOID THIS ERROR: Preparing in a disorganized way.

    Too many candidates do not write and execute a plan for their VCDX preparation.  Quantity of preparation is no substitute for quality. I have seen candidates who spent many hours in preparation, only to fail; their preparation was haphazard and random.

    One advantage of having a preparation plan is that you can spread the workload over many days. Another advantage is that you are less likely to forget particular steps of preparation, such as might be suggested by the above documents and by the VCDX Blueprint.

    A final advantage of having a preparation plan is that you'll be able to sleep better the night before the defense.  See above.

  5. AVOID THIS ERROR: Making it difficult for the panelists to score you.

    I have seen many unsuccessful candidates insist on rephrasing panelists' questions before answering them. This behavior uses up precious seconds, and it also raises the cognitive burden on the panelist as he or she attempts to choose a score. Neither of those phenomena works in the candidate's favor.

    Panelists will often ask open-ended questions: "How would your design have been different if...?" Unsuccessful candidates treat questions like this as mere mine-fields, where the best possible outcome is to avoid making a mistake. But successful candidates use open-ended questions to display their skills in the areas defined by the blueprint.

    Another variety of this error has to do with the design scenario. Some candidates assume that the design scenario is some kind of trick. After all, in a real design exercise, 30 minutes wouldn't even be enough time for one stakeholder interview!  Indeed, you'd spend much more than 30 minutes before you ever opened Visio.

    The design scenario is the candidate's opportunity to show samples of how he or she approaches design: not just the discovery phase, but also the conceptual, logical, and physical designs.  To succeed in this activity, you must be willing and able to propose tentative design components based on incomplete information, and refine as you learn more.

  6. AVOID THIS ERROR: Having holes in your fundamental knowledge.

    Among the questions a candidate will be asked are some that might seem elementary. But past candidates have, during defense, displayed surprising holes in their knowledge of logical or physical design and/or vSphere technology. Although it is impossible to disqualify oneself from VCDX with any single defense error, these errors certainly make the panelists' decisions much more difficult.

    Here are two sample errors like this.

    • Not knowing that, in vSphere 4 HA, allowing a cluster to have more than four of its hosts in the same blade enclosure creates a single point of failure.
    • The belief that VMFS block size should be tuned for performance much as NTFS or ext3 are (big block sizes for sequential I/O, small for random).

    Of course, an exhaustive list of this kind of error is impossible. The way to guard against having embarrassing holes in your knowledge is to socialize your knowledge. Don't be afraid of making erroneous statements in front of your peers. Seek peer review of your designs and your design explanations.

    If you are able to attend VMworld, take part in the "Mythbusters Goes Virtual!" session, or watch the recording later.

  7. AVOID THIS ERROR: Preparing a 75-minute PowerPoint presentation, and expecting to present it and be judged on how well you present it.

    The presentation you bring to your defense is merely a structuring device, meant to start conversations. Plan a presentation of your design that will help you explain it. Avoid going into depth in the presentation itself; detail will arise from discussion. The duration of the presentation, if you were to deliver it uninterrupted, should be about 15 minutes.  But expect to be interrupted. Expect the interruptions to be more important than the slides.

    Candidates who insist on presenting every slide in their decks, on their own terms and pace, are committing the "Making it difficult for the panelists to score you" mistake noted above.

These are the most important errors.  Here are some further tips to help you avoid other mistakes.

  1. Don't have animated transitions among your slides. Those 2-second crossfades will waste precious time.
  2. If a diagram is important, include it in your deck, to save you the time of whiteboarding it.
  3. Don't be afraid of the whiteboard.
  4. Don't be afraid to say "I don't know."  See the FAQ for Unsuccessful VCDX Candidates for more information on this.
  5. Don't debate the ground rules of the defense session. Although imperfect, they are the same for all candidates, and they provide a level playing field.
  6. Don't waste time with a detailed presentation of your résumé or curriculum vitae. Your recitation of your career history will neither score you points nor cost you points.
  7. Don't tell jokes. Although there is no prohibition against being funny, using up time solely for humor is wasteful.
  8. Stop to breathe every so often.
  9. Find a way to make it fun.

The goal of the VCDX program is that every candidate who makes it to the defense session passes. No aspect of VCDX is made arbitrarily difficult. Instead, the program aims to be beneficial to successful and unsuccessful candidates. Attention to the items in this posting will help you in your career, regardless of which category you eventually find yourself in.

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2 Replies

These are great, Brian!  Keep it up!

--Matt VCDX #52
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One more tip I would like to share.  Another common pattern I see in unsuccessful candidates is that they haven't spent much time thinking about the risks inherent in their design.  What could go wrong?  For a given risk, how likely is it, and what would the impact be if the Bad Thing happened?  How did you mitigate each risk, or else why did you decide to accept it?  For those risks you accepted, how would you have mitigated them if the customer had more budget?

Thinking about risks is also beneficial for VCDX candidates because it forces them to refresh their awareness of the pros and cons of their design decisions.

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