Yellow Bricks

by Duncan Epping

Various

22 / 23 May 2018 – VMware Technical Support Summit

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A while back I was asked if I could present at the VMware Technical Support Summit and last week I received the agenda. I forgot to blog about it so I figured I would share it with everyone. I was supposed to go to this event last year but I had a clash in my calendar unfortunately. At this event organized by our support team you will have the ability to sit in some extreme deep dive sessions. Below you can find the agenda, and also here’s the registration link if you are interested! Note that Joe Baguley will be doing a keynote, and Cormac Hogan and I will be doing a session on vSAN futures!

vSAN Stretched Cluster: PFTT and SFTT what happens when a full site fails and multiple hosts fail?

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This question was asked on the VMTN community forum and it is a very valid question. Our documentation explains this scenario, but only to a certain level and it seems to be causing some confusion as we speak. To be honest, it is fairly complex to understand. Internally we had a discussion with engineering about it and it took us a while to grasp it. As the documentation explains, the failure scenarios are all about maintaining quorum. If quorum is lost, the data will become inaccessible. This makes perfect sense, as vSAN will always aim to protect the consistency and reliability of data first.

So how does this work, well when creating a policy for a stretched cluster you specify Primary Failures To Tolerate (PFTT) and Secondary Failures To Tolerate (SFTT). PFTT can be seen as “site failures”, and you can always only tolerate 1 at most. SFTT can be seen as host failures, and you can define this between 0 and 3. Where we by far see FTT=1 (RAID-1 or RAID-5) and FTT=2 (RAID-6) the most. Now, if you have 1 full site failure, then on top of that you can tolerate SFTT host failures. So if you have SFTT=1 then this means that 2 host failures in the site that survived would result in data becoming inaccessible.

Where this gets tricky is when the Witness fails, why? Well because the witness is seen as a site failure. This means that if you have lets say 2 hosts failing in Data Site A and 1 host failing in Data Site B, while you had SFTT=2 assigned to your components, that your objects that are impacted will become inaccessible. Simply because you exceeded PFTT and SFTT. I hope that makes sense? Lets show that in a diagram (borrowed it from our documentation) for different failures, I suggest you do a “vote count” so that it is obvious why this happens. The total vote count is 9. Which means that the object will be accessible as long as the remaining vote count is 5 or higher.

Now that the witness has failed, as shown in the next diagram, we lose 3 votes of the total 9 votes, no problem as we need 5 to remain access to the data.

In the next diagram another host has failed in the environment, we now lost 4 votes out of the 9. Which means we still have 5 out of 9 and as such remain access.

And there we go, in the next diagram we just lost another one host, in this case it is the same location as the first host, but this could also be a host in the secondary site. Either way, this means we only have 4 votes left out of the 9. We needed 5 at a minimum, which means we now lose access to the data for those objects impacted. As stated earlier, vSAN does this to avoid any type of corruption/conflicts.

The same applies to RAID-6 of course. With RAID-6 as stated you can tolerate 1 full site failure and 2 host failures on top of that, but if the witness fails this means you can only lose 1 host in each of the sites before data may become inaccessible. I hope this helps those people running through failure scenarios.

Confessions of a VMUG Speaker – the prequel #SpeakerFail

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On twitter a question was asked by Casey West if people had “Speaker Fail” stories and I replied to it with my story. I have told this story to some folks but never shared it on my blog, so I figured I would share it. I already wrote an article about speaking at your local VMUG and what to do and not to do, but these are things I found out the hard way…

So what is the back story? Well, many many years ago I just started working for VMware. I was already doing some blogging and had posted a bunch of articles about vSphere HA. As a result I knew some of the developers and one of them asked me to work with him on the deck. I was terrified of public speaking, actually I rejected other public speaking, but I figured that helping him out develop the deck couldn’t hurt. So I worked with him on the deck and after a while he asked if I wanted to help presenting the deck.

I thought about it for a while and my brain said: SAY NO. I gave it some more thought, and although I was terrified I wanted to go outside of my comfort zone, I didn’t realize though when I said yes that I would go in to the panic zone straight away instead of in to the “learning zone”. I was nervous, extremely nervous. But luckily the developer told me that it would only be a session in front of 100 people.

A couple of weeks go by and I receive an email. The developer told me that due to various escalations/bugs had to fix for an upcoming release he could not fly to the event. I was by myself. You can imagine that my level or nervousness went up with about 10x. I would be on my own in front of 100 people, what now? The VMworld team transferred the session on to my name, and then I logged in to the backend to see the details of my session. This includes the registrations. Hold on, it was supposed to say 100 people, but it says 450. WHAT? 450 people in a single room? And then a day they changed rooms for the sessions, as it was overbooked, quickly after that the registrations filled up to 700 something. I was nervous just thinking about presenting in front of 100 people with a co-presenter, now I was going up on stage by myself in front of 700+.

I rehearsed, rehearsed, rehearsed, rehearsed and rehearsed. I wanted to make sure I knew every slide inside out before I went up on stage. And I did, I was nervous as hell but I knew my slides by the letter. Unfortunately I was so nervous that I went in to this “hyper sensitive state” and I could hear everything that was going on in the room. After 3 or 4 slides I was explaining a complex diagram and someone’s phone went off, he picked it up and walked out. I lost my train of thought and had to start over again with the slide. Which in its turn made me over more nervous. It took me roughly 5 minutes just to recover from that, but it felt like days. I finished my session and decided I would never ever present again. I am writing this while presenting at a VMUG, no need to tell you that I didn’t give up.

For those who have been in this situation, or are hesitant to present because of these reasons, please read the post Confessions of a VMUG speaker, which was written before this post. I hope it helps realizing people that many people face the same fears, but by practicing your session and doing it over and over again at various events you will become better and it will make it easier. Heck, you may even start to enjoy it after a while!

 

VMworld Call For Papers opened, some tips…

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For the past 8 years or so I have presented at VMworld, I think I have submitted sessions for the past 10 years or so. I probably submitted well over 60 sessions, and I mean “WELL OVER”. Many of course which got rejected. Some for which I understood why they were rejected, others for less obvious reasons as to me the session(s) sounded awesome. Then again, that is part of the problem: to me. I am usually not the person deciding which session is in and which session is out. Plus, it is easy to forget but there are literally thousands of submissions, and most of which sound very similar unfortunately, which also means that the majority of people submitting a session will unfortunately  receive the “rejected” email.

Then there’s the bigger problem: we also have many VMware people submitting sessions, and although it may not sound fair, they usually get picked over community sessions. Unless you are a thought leader in the space you submitted a session for, an example here for instance would be people like Chris Wahl and Jason Nash. They presented on Distributed Switches / VMware networking a couple of times. They are known in the industry and presented at various VMUGs, and killed it at VMworld a couple of times, which was to be expected based on their reputation.

Let’s be honest here for one second, some people may act surprised their session did not get picked and a similar sounding session by a VMware person did, but it makes sense right? Most VMware folks are experienced, have done these kind of events many times, and as such the person picking knows it is the safest bet. Heck, even within VMware there’s some sort of ranking, let’s assume a new version of vSAN is released around VMworld, if a Consultant, Pre-Sales Engineer, Product Marketing Manager and Tech Marketing Manager submit a similar sounding technical session then most likely the Tech Marketing Manager will get the session. Why? Well, that is his job: create and present technical collateral for the product. Safe bet right? However, if the developer submits a session then he/she will most likely get it. Sounds fair right? Now that we got that out of the way, lets focus on your submission. What works, and what does not work? Is there a

First of all: Experience. If you have no experience in public speaking, why are you submitting for the largest virtualization conference world wide? Each speaker will need to provide their experience, I can tell you that when I voted for VMworld submissions this was always something I looked at. If you have no experience whatsoever then you are aiming too high. Go to your local VMUG first, get some sessions under your belt. Start small and work up to some “larger” rooms, at VMworld it is not uncommon to have 700 – 1200 people in your room. Without experience that may end up being a very painful exercise, and it is not a risk which I (as a person who voted) was willing to take.

Secondly: Topic. Come up with a good topic, potentially try it out even at a local VMUG or even test the idea against some colleagues. It needs to be something you are passionate about and (preferably) an expert in. Look around you if you know anyone else who likes talking about the same topic. Can you join forces maybe? Even better, do you know a VMware employee who may be interested in co-presenting? And if so, what can they bring to the table that spices up your session? (Deep dive details for instance.) Try to make sure your topic is “unique”, and as a community member / customer / partner try to add something that we as VMware employees are challenged with: your experience as a “user / implementer / architect”. Make sure this is crystal clear in your abstract, and of course make sure your abstract is catch and does your session justice. Don’t make it too long, if the person voting needs to read for 15 minutes to understand what your 60 minute session will be about you did something wrong.

Thirdly: Title. I was only joking when I said on twitter that the title for my proposed session was “Deep Dive in Artificial Intelligence delivered by Green IoT solutions using Machine Learning in a Blockchain world enabled through the power of containers scheduled by Kubernetes running on HCI provided by VMware vSAN in VMC on AWS“. Although I still may want to submit it, as it is already overbooked according to the VMware twitter account ;). Either way, try to keep it short and make crisp and catchy, and adding a buzzword may help but don’t start buzzword bingo like I did. I usually revise my titles 4-5 times before I submit. It needs to represent the abstract accordingly, and it needs to draw attention if you want your session to be picked from the thousands being submitted.

I hope that helps a bit, in the early years I would always submit around 6 sessions, but my strategy now is definitely: quality over quantity. Work on creating the abstracts and titles for 3 great sessions and submit those, instead of taking a shotgun approach and submitting 6+ half baked sessions… Good luck, and remember: if you don’t end up getting selected, submit the proposal to a VMUG near you instead. They are always begging for community sessions. Good luck.

Coming to a VMUG in EMEA near you…

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I just came back from the VMUG in Denmark, which was a great event, and I figured I would share what I have planned right now for the upcoming months. I hope to be able to meet many of my readers at one of these events. If you are there, don’t be afraid to stop by and say hi! I am also more than happy to take back any feedback you have on storage/availability to our engineering and product management teams! (Oh and if you are a VMUG leader in EMEA and you would like to have my speak at one of your events, just drop me an email.)

Here we go:

  • 22 Feb – Newcastle, UK VMUG
  • 7 March – Lausanne, Switzerland VMUG
  • 8 March – Zurich, Switzerland VMUG
  • 20 March – Den Bosch, Netherlands VMUG
  • 10 April – Istanbul, Turkey VMUG

See you there!