My ramblings about all things technical

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VMware Knowledge Nuggets – Percentage of Host Resources Admission Control

As started and introduced in my introductory posting around the VMware Knowledge Nuggets I am posting compact VMware knowledge nuggets which I hope will show people some unknown features or things they need to think about around choosing features and maybe even get some good discussions going via the comments section.


Using Percentage Based Admission Control and the usage of das.vmMemoryMinMB and das.vmCpuMinMHz.

This discussion stemmed  from the twitter discussion I had with Ed Grigson a few weeks back as mentioned in my first posting (albeit a tangent off of it) . I commented that even if you use percentage based admission control it is still a good idea to configure the das.vmMemoryMinMB and das.vmCpuMinMHz advanced settings to provide a better idea when HA is doing the math for admission control and prevent overcommitment with a specified minimal amount of resources for each virtual machine.


Rather than re-cover what has been done and explained so well,  the following two postings from Duncan Epping and Josh Odgers respectively cover it perfectly


Using das.vmmemoryminmb with Percentage Based admission control

Example Architectural Decision – VMware HA – Percentage of Cluster resources reserved for HA


Certainly something to keep in mind when doing designs and even something that you may determine is good to add to your existing environment. Although remember that admission control is not about resource management as described really well by Duncan Epping in his article here. Funnily enough I think a discussion I had with Duncan at the 2011 Europe VMworld around a customer using reservations with percentage based admission control for resource management caused him to create the posting.

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VMware Knowledge Nuggets

Over the past few weeks I have had several discussions around VMware features and technologies via twitter where someone asked a question or made statement around a VMware vSphere feature and the subsequent discussions seemed to shed some light on things people either didn’t know or had forgotten.


So my idea is to create a series of blog postings trying to cover compact VMware knowledge nuggets which I hope will show people some unknown features or things they need to think about around choosing features and maybe even get some good discussions going via the comments section.


Does excluding VMs from HA exclude them from admission control calculations?

This question was posted by fellow London VMUG attendee Ed Grigson a few weeks back via twitter as shown below




Due to my aiming to reattempt my VCDX defence soon I have been reading and learning as much as is possible and had come across the answer to this during my reading of Duncan Epping and Frank Denneman’s vSphere 5.1 Clustering Deepdive book and responded to Ed with the answer which is No. Even if it is disabled within HA, it is still included in admission control calculations. So be mindful of leaving machines lying around in your cluster as depending of your admission control policy this could have varying impacts on your ability to power on machines.

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What’s New In vCloud Automation Center 6.1

Not long after VMworld Europe vCAC 6.1 was released. For the past year I have been very fortunate to have been on some very large vCAC projects as an extension of VMware PSO and have seen the product change dramatically. there have certainly been some challenges but I’m super excited about vCAC 6.1 and from the experience I have gained of it so far it is looking very solid and now can work seemlessly with vCO along with a number of other great new feaures. So below is an overview of what is new in vCAC  6.1.

vCAC Extension





Interested in Developing a VCO Plugin?
Free Access to the vCO Plug-in SDK

  • The SDK has samples and documentation to facilitate development
  • Additional Resources

    Distribution on VMware Solutions Exchange
    – Contact: Meenakshi Nagarajan for additional info



    Automating Application and Infrastructure Services

    Simplifying the deployment and management of single machines and complex multi-tired applications.






    User Experience






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    VCAP5-DCA: Objective 4.1

    Implement and Maintain Complex VMware HA Solutions

    There isn’t much that is different for this over what was in the VCAP4-DCA Blueprint objective. I’ve been watching the HA videos from the Trainsignal VMware vSphere 5 Training course and the vSphere 5 Clustering Tech Deepdive book by Frank Denneman and Duncan Epping. Due to HA and DRS being revamped for vSphere 5 I think the book covers it all perfectly and more. Duncan also did a blog posting covering HA here: (it’s a serious deepdive)


    • Identify the three admission control policies for HA
    • Identify heartbeat options and dependencies

    Skills and Abilities

    • Calculate host failure requirements
    • Configure customized isolation response settings
    • Configure HA redundancy

    Management Network – Simply down to setting two management connections/vmkernel ports

    Datastore Heartbeat – this is new to vSphere 5 and is therefore something new to this objective. I’ve learnt it via the clustering tech deepdive book and from this blog posting by Duncan It is also covered in the trainsignal videos and is something you should know from your VCP5 studies

    Network partitions – This is also new and is covered in the book and the deepdive posting. I also learnt how to fix it should a host alert that it is network partitioned as I think this could be a task and so I learnt this kb article it is also covered here

    • Configure HA related alarms and monitor an HA cluster
    • Create a custom slot size configuration
    • Understand interactions between DRS and HA
    • Analyze vSphere environment to determine appropriate HA admission control policy
    • Analyze performance metrics to calculate host failure requirements
    • Analyze Virtual Machine workload to determine optimum slot size
    • Analyze HA cluster capacity to determine optimum cluster size

    Due to objective 3 having DRS as objective 3.3 and this objective being about HA it has worked in well that I have been re-reading the vSphere 5 Clustering Tech Deepdive book as it covers both of these 100%. All that you need to do now is practice doing it all in your lab


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    All Things Virtual 20


    There have been some brilliant blog postings since my last All Things Virtual,the release of some great news for android phones and a book written by two of the top VMware professionals in the world. If this is the first time you are reading one of my All Things Virtual then the idea of the posting is a quick post up of all the things virtual and linked to virtual that I have been doing/working with/learning/reading up on in the past few weeks.

    • Frank Denneman of fame and Duncan Epping of fame have written and released the vSphere 4.1 HA and DRS technical deepdive book. These two guys are probably the two best people in the fields of DRS and HA with Duncan having the very successful and extremely in-depth HA Deepdive and DRS Deepdive postings on his blog as well Frank having some of the best postings on DRS on his blog. I have ordered the book already and am awaiting its arrival. Both Duncan and Frank have already covered what is in the book in such detail that I feel it’s pointless to rehash what they have already said so here is Duncan and Franks postings about the book. I look forward to reading through the whole book when it arrives and strengthening my knowledge on the two technologies.
    • As I’ve said a few times before I enjoy testing myself by trying to obtain certain certifications, not to be a certification collector but to set goals to try to continually push myself and strengthen my knowledge and not sit still. So the release of the new certifications by EMC really caught my attention as I’m currently trying to strengthen my knowledge on storage technologies and practices by doing the ISM(Information Storage and Management) course. One of the perks of working for EMC is I’m able to do the course as a e-learning course for free and with the release of the new EMC Cloud Architect certifications the first step is obtaining your Information Storage and Management Associate (EMCISA) certification which fits in perfectly to my study goals for 2011. To make sure I don’t explain it incorrectly I would recommend reading Chuck Hollis’ blog where he has detailed the new certifications.
    • Speaking of certifications I’m really pleased by the amount of traffic my VCAP-DCA&DCD Study Resources Page and my VCP Study Resources Part 1 and Part 2 pages are receiving. Thanks to everyone who has linked to it/tweeted about itclip_image001. One of the main resources listed in my VCAP-DCA study resources is Sean Crookston’s VCAP-DCA Index. Sean has now written the exam and has posted a brilliant write up on his impressions of the exam here. Rynardt Spies has also recently written the exam and posted his impressions here. I’ve decided to try sit the exam by March/April next year as I’m not likely to be ready before I go on holiday next year and have learnt from experience that writing an exam just before I go on holiday isn’t a good idea.
    • Next is one of my blog postings of the year due to its depth of information and brilliant supporting links and documents to cover his claim. It’s a blog by Julian Wood (@Julian_wood) all about how he feels vCenter is letting VMware’s side down. I would highly recommend everyone read it as it is both amusingly true to anyone looking after a virtual environment and covers many of the obstacles you may hit in the future with your own virtual centre server so you can be as prepared as possible if you are implementing any of the technologies. I agree with what Julian is saying and do think VMware need to make a plan with virtual centre as there are far too many bugs and problems still with virtual centre and for something that is so integral to the smooth working of your virtual environment it really needs to be as solid and reliable as possible.
    • With the release of PowerCLi 4.1 it is now possible to manage permissions with PowerCLI. The VMware blogs have covered all the new capabilities and how to do them here. I’m busy trying to teach myself PowerCLI by trying to do as much of my daily work with PowerCLI and VMA due to a large part of the VCAP-DCA exam being based on you knowing how to do things via these tools. Seeing as I’m a point and click person these are skills I need to learn very quickly and be able to do it as second nature.
    • One of the new features of vSphere 4.1 is VAAI (vStorage API’s for Array Integration). Recently both Duncan Epping and Eric Sloof have posted brilliant information on this feature and in Eric’s case have attached a video detailing how it all works. These are great for anyone who is working with VMware technologies and is likely to be either using vSphere 4.1 or will be upgrading to vSphere 4.1.
    • One of the biggest technologies to come out in virtualisation this year is VMware’s vCloud Director. It was the lab that was taken the most at VMworld Europe and everyone is trying to learn about it seeing as it is VMware’s product to help you move your resources into the cloud. I too did all the vCloud Director labs at VMworld Europe and have been collecting as many top postings about vCloud Director as possible so I can fully understand it so when I’m asked to implement it I’ll know how. Two blog postings have been added to this list from the past few weeks; one is from David Davis of Trainsignal fame interviewing the infamous Scott Lowe and was posted on the VMware blogs page interviewing Scott on Cloud Computing and vCloud Director. This posting really got my attention as it was really interesting to me to learn more about how the technologies from EMC and the VCE are perfect to help you move as smoothly as possible to the cloud, especially seeing as I work at EMC so I really should know about all of thisclip_image001[1]. Next is an amazing demo by Duncan Epping that he created for the Dutch VMUG all about vCloud Director, creation of an Organization and its resources this demo is exactly what I love to watch and learn from as I’ve only recently been able to install vCloud Director in my home lab so it’s great to see how it’s all done and seeing as vCloud Director is such an in-depth and complex product any resources to shed some light on different things about how things are done within it are greatly appreciated by myself. I know I said two but if you missed me mentioning this in one of my previous postings and want to learn more about vCloud Director then look at the resources Scott mentioned in his interview and have a look at Hany Michael of fame’s vCloud Director page. Hany also has great video on vCloud director and his posting on VMware vCloud Director in a Box is what I used to setup my lab environment.
    • Next is the announcement of the Partnership between VMware and LG to virtualise android smartphones for usage by business users. Mobile virtualisation has been spoken about for quite a while but this next step is very exciting and as one of my colleagues Jaspal Dhalliwal posted that Virtualization is Coming of Age now and means VMware is going from servicing a few hundred thousand people to tens of millions of people via their smartphone devices. Simon Long also posted about this announcement on his page and has posted a very cool video of it. I’m not a massive phone person to be honest, I don’t have a smartphone or an iPhone but watching tat video is really making me think of getting myself one very soon.
    • Last but not least is the announcement by Veeam that they are giving away free NFR keys to VCPs, VCIs and vExperts. This is a brilliant idea and it shows that Veeam know who their dedicated followers are and who is likely to give them great press about the products and help them gain even more popularity. I’ve already downloaded mine and am due to install it into my lab environment very soon. If you’re a VCP/VCI or vExpert then get yourself a copy before they stop the deal.

    Well that’s everything that has been on my to read list and all the news that has caught my interest.


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    All things virtual XI

    I’m fairly pleased that these summaries of the things that have caught my interest in virtualisation have been getting so much traffic and even more pleased is that even though I didn’t post anything massive in particular I got my highest number of viewers last month to this blog with a week still to go which is always encouraging as hopefully some of the stuff I write about helps someone like so many of the websites I read have helped me.

    First is the imminent announcement of the vExperts for 2010. I would obviously be extremely honoured if I became one but I think I’d be in shock a lot more though as there are some really top people in the field.

    Next is a posting by Gabrie van Zanten (@gabvirtualworld) all about the default installation settings he does when setting up a vSphere 4 host. Some of the tips he mentions are ones I never thought about or knew so I’ll definitely be referencing his posting as well as Duncan Epping’s response to Gabrie’s posting all about his best practices/recommendations. I always enjoy finding these kinds of postings as sometimes these kinds of things you only learn having done many high level environment deployments etc and are also great tips for thoughts for my builds for my future VCDX attempt.

    Duncan has also done a two part blog posting with Frank Denneman all about swapping in your VMware environment and what metrics actually show performance degradation and how they are worked out. Franks posting gives more of a description on how the memory is calculated and describes the reasons for swapping happening in your environment and how to try avoid it happening and thereby impacting your servers performance.

    A few people have blogged about this but the first i saw it was on Virtualization spotlight a blog by Patrick Redknap. VMware have published a video KB on how to power off an unresponsive VMware ESX virtual machine. This video is a really useful one as quite a number of times I’ve battled to get a vm to shutdown correctly even after having tried rebooting services it stayed hung.

    Frank Denneman has also posted a really good posting all about setting up memory reservations in your resource pools and how they work. This posting ties in really well on the little known (at least to me and a number of people I have spoken to /asked about memory reservations) about how a vm’s reservations will hoard memory if it has been used by the virtual machine once. Frank describes it well in the part “Even if the virtual machine becomes idle, the VMkernel will not reclaim this memory and return it to the free memory set. This means that ESX can start swapping and ballooning if no free memory is available for other virtual machines while the owning VM’s aren’t using their claimed reserved memory.” Recently while doing some testing for the HA setup in my environment I noticed from a vCheck report I ran that HA stated there were no spare slots in my HA cluster, so I did some research and came across Duncan Epping’s Slot sizes posting and onto his HA deepdive posting in which he describes how the slots are worked out :

    “To calculate available resources and needed resources for a fail-over HA uses a concept called “slots”. Slots dictate how many VMs can be started up before vCenter starts yelling “Out Of Resources”!! Normally each slot represents one VM.

    A slot is a logical representation of the memory and CPU resources that satisfy the requirements for any powered-on virtual machine in the cluster.

    In other words a slot size is the worst case CPU and Memory reservation scenario in a cluster. This directly leads to the first “gotcha”:

    HA uses the highest CPU reservation of any given VM and the highest memory reservation of any given VM. If no reservations of higher than 256Mhz are set HA will use a default of 256Mhz for CPU and a default of 0MB+memory overhead for memory.

    If VM1 has 2GHZ and 1024GB reserved and VM2 has 1GHZ and 2048GB reserved the slot size for memory will be 2048MB+memory overhead and the slot size for CPU will be 2GHZ. “

    So I went through all of my vm’s and found a few stragglers that had memory reservations that had been switched off for a while. Once i cleared these our empty slots went from zero to 85 due to two of the switched off machines having six gb’s of ram reservations. Eric Sloof has also recently posted a great posting all about adding resource pools and how these can impact the performance of your vm’s even if you think they aren’t.

    Speaking of VMware clustering options Cody Bunch has done a brilliant posting in the math behind the DRS stars. The math is a bit over my hear personally but math always has been so nothing new there. It’s very interesting how they work all these things out and a great bit of information for your setting up your DRS cluster.

    Whilst i was doing my HA testing i had a few questions of how HA works and due to our environment being a test lab it’s also an integral part of our work as a consultancy so I couldn’t test what happened for the differing options you can select for HA. So I asked on twitter and Kendrick Coleman (@kendrickcoleman) not only replied to me among other people but went and tested it out for me in his test lab and posted a very nice blog posting all about it. Glad I gave him an idea and thanks for the results Kendrick!! It’s much appreciated and is one of the reasons being on twitter is priceless if you work in IT.

    If you want to  comment about my blog either leave me a comment and I’ll make sure I respond to you or add my on twitter via @greggrobertson5. Also congrats to the imminently crowned vExpert’s for 2010.

    Gregg Robertson