Yellow Bricks

by Duncan Epping

VMware

HA role promotion…

· ·

I received a very valid question this week from someone who bought our book. The question was as follows:

On Page 35 it is mentioned that a Secondary Node is not automatically elected as a Primary if a Primary fails. It then goes on to state the conditions under which this does occur, one of these is if the primary node becomes disconnected from the Cluster. When an ESX host fails doesn’t it always end up in the “disconnected” status, if so why isn’t the role transferred?

This one had me thinking for a couple of minutes as it was 6 months ago that I wrote that section, but I knew I tested this back then. When a host fails it will not receive the status “disconnected” but it will receive the status “not responding”. You can disconnect a host by right clicking it and selected “disconnect from cluster”, that would transfer the role to another node… in the case of “not responding” this doesn’t happen as vCenter is unaware of what happened to the host.

Shares set on Resource Pools

· ·

During our session at the Dutch VMUG Frank was explaining Resource Pools and the impact of limits and reservations. As I had the feeling not everyone in the room was using resource pools I asked the following questions:

  1. How many people are using Resource Pools today?
    • Out of the roughly 300 people who attended our session 80 showed their hands. The follow-up question I asked was…
  2. How many people change the Shares setting from the default?
    • Out of those 80 hands roughly 20 people raised their hands and that lead me to the next question…
  3. How many people change the Shares value based on the amount of VMs running in that Resource Pool?
    • Now only a handful of people raised their hand.

That is what triggered this post as I believe it is an often made mistake. First of all when you create a Resource Pool there are a couple of things you can set a reservation, a limit and of course shares. For some reason shares are often overlooked. There are a couple of things I wanted to make sure everyone understands as judging by the numbers of hands that were raised I am certain there are a couple of common misunderstandings when it comes to Resource Pools:

  • If you create a Resource Pool a default Shares value is defined for the resource pool on both Memory and CPU
  • Shares specify the priority of the resource pool relative to other resource pools on the same level

This means that even if you don’t touch the shares values they will come into play whenever there is contention. This also means that the resource allocation on a VM level is dependent on the entitlement of the resource pool it belongs to.

Now what is the impact of that? I guess I should quote from the “The Resource Pool Priority-Pie Paradox” blog post my colleague Craig Risinger wrote as it clearly demonstrates the issues that can be encountered when Resource Pools are used and Shares values are not based on the relative priority AND the amount of VMs per pool.

“Test” 1000 shares, 4 VMs => 250 units per VM (small pie, a few big slices):

“Production” 4000 shares, 50 VMs => 80 units per VM (bigger pie, many small slices):

I guess this makes it really obvious that shares might not always give you the results you expected it would.

Another issue that could arise is when Virtual Machines are created on the same level as the Resource Pools…. Believe me it doesn’t take a lot for a single VM to have higher priority than a Resource Pool in times of contention.

Again, whenever you create a Resource Pool it will “inherit” the default shares value, which equals a 4vCPU/16GB Virtual Machine, and whenever there is contention these will come into play. Keep this in mind when designing your virtual infrastructure as it could potentially lead to unwanted results.

VMware HA Deployment Best Practices

· ·

Last week VMware officially released an official paper around Deployment Best Practices for HA. I was one of the authors of the document. Together with several people from the Technical Marketing Team we gathered all best practices that we could find, validated and simplified them to make it rock solid. I think it is a good read. It is short and sweet and I hope you will enjoy it.

Latest Revision:
Dec 9, 2010

Download:
http://www.vmware.com/files/pdf/techpaper/VMW-Server-WP-BestPractices.pdf

Description

This paper describes best practices and guidance for properly deploying VMware HA in VMware vSphere 4.1.  These include discussions on proper network and storage design, and recommendations on settings for host isolation response and admission control.

vCloud Director Demo, creation of an Organization and its resources

· ·

At the Dutch VMUG I presented two sessions. One was about HA/DRS and the other was about vCD. The vCD session contained a live demo and as a backup I decided to record the demo just in case for instance the internet connect would go down. The video shows the creation of an Organization, Org vCD, Org Network and of course a vApp. I didn’t want the video to go to waste so I decided to share it with all of you. I hope you will enjoy it.

vSphere 4.1 HA and DRS Technical Deepdive, the book!

· ·

In August we announced that we were working a secret project and let you guys in on it. The idea was to get it published through an official Publisher but due to several circumstances and a very tight deadline we decided to go the self-publishing route to make it available as soon as possible. So here it is, the moment both Frank Denneman and I have been waiting for…. it is finally available, the HA and DRS technical deepdive.

As of today “vSphere 4.1 HA and DRS Technical Deepdive” is available on paper via CreateSpace and Amazon. We are also working on getting a digital copy up for sale but that will more than likely be early 2011.

There is something I want to make very clear here as I have heard multiple people referring to this book as “Duncan’s Book”. This book was very much a joint effort. Frank has invested at least as much time in this project as I have, and probably even more. I want to thank Frank for his hard work and hope everyone realizes that it is our book and not my book!

We want to take the opportunity to thank our Technical Reviewers for their very valuable feedback and for keeping us honest; fellow VCDX Panel Member Craig Risinger (VMware PSO), Marc Sevigny (VMware HA Engineering), Anne Holler (VMware DRS Engineering) and Bouke Groenescheij (Jume.nl). A very special thanks to Scott Herold for writing the foreword!

For those who can’t wait, order it via CreateSpace or Amazon now. (Please be so kind to leave a review

This is the description of the book that is up on CreateSpace/Amazon:

About the authors:
Duncan Epping (VCDX 007) is a Consulting Architect working for VMware as part of the Cloud Practice. Duncan works primarily with Service Providers and large Enterprise customers. He is focussed on designing Public Cloud Infrastructures and specializes in bc-dr, vCloud Director and VMware HA. Duncan is the owner of Yellow-Bricks.com, the leading VMware blog.
Frank Denneman (VCDX 029) is a Consulting Architect working for VMware as part of the Professional Services Organization. Frank works primarily with large Enterprise customers and Service Providers. He specializes in Resource Management, DRS and storage. Frank is the owner of frankdenneman.nl which has recently been voted number 6 worldwide on vsphere-land.com

VMware vSphere 4.1 HA and DRS Technical Deepdive zooms in on two key components of every VMware based infrastructure and is by no means a “how to” guide. It covers the basic steps needed to create a VMware HA and DRS cluster, but even more important explains the concepts and mechanisms behind HA and DRS which will enable you to make well educated decisions. This book will take you in to the trenches of HA and DRS and will give you the tools to understand and implement e.g. HA admission control policies, DRS resource pools and resource allocation settings. On top of that each section contains basic design principles that can be used for designing, implementing or improving VMware infrastructures.
Coverage includes:

  • HA node types
  • HA isolation detection and response
  • HA admission control
  • VM Monitoring
  • HA and DRS integration
  • DRS imbalance algorithm
  • Resource Pools
  • Impact of reservations and limits
  • CPU Resource Scheduling
  • Memory Scheduler
  • DPM

We hope you will enjoy reading it as much as we did writing it. Thanks,