Yellow Bricks

by Duncan Epping

ha

Did you know? vCloud Director Reservation Pool allocation model fact

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I did not know about this, but someone pointed this out last week and I figured it was worth blogging about as this feature can potentially impact your design. (Think HA admission control policies and resource management)

When you create a VM in an Org vDC which is defined as a Reservation Pool you can actually manually set the shares per type of resource (memory and CPU) and also set a reservation and even a limit if and when needed. Pretty cool, but as you can imagine also very complex at some point to figure out to what it should be set.

VMware HA Deployment Best Practices

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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.

European distributor for the HA and DRS Technical Deepdive

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Frank published the following yesterday, but as many people have asked me about this I thought I would post it as well. For those who were looking for a European distributor of our book:

As of today, our book “vSphere 4.1 HA and DRS Technical Deepdive” can be ordered via ComputerCollectief. Computercollectief is a dutch computer book and software reseller and ships to most European countries. Using Computercollectief, we hope to evade the long shipping times and accompanying costs.

Go check it out. http://www.comcol.nl/detail/73133.htm

Comcol expects to be able to deliver at the end of this month.

HA without DRS?

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I had question on my HA Deepdive which I thought was worth answering in an article:

How does the active primary node decide where to restart failed VMs? Does it use a round-robin algorithm for selecting a host to start the VMs in restart priority order? What happens if the remaining nodes are imbalanced, especially without DRS enabled; are the nodes that have no spare capacity skipped? Or, does the active primary node restart VMs on the least busy host first, then the next busy host, etc?

Also, if VMs have no reservation for CPU or memory set, how does HA decide the number of VMs to restart on any one node? Is it possible that HA will restart too many VMs on one node so that performance is extremely poor until DRS move some VMs to other nodes?

In the past HA(pre 4.1) would consider the utilization of the Hosts and go through a check for every VM that needs to failover. It would fail the VM over the host with the most amount of available resources. Now from a “latency” perspective that is not the best approach as you can imagine. With latency meaning the time it takes to restart the VMs and the delay caused by hostd. Now type of delay can be cause by hostd? Well lets assume you have 1 host which is not doing a lot, this host would be the host that is selected for most failovers. Having 10 VMs (or more) starting in parallel will beat hostd severely.

So does HA use DRS to select which host to use for the restart? No it won’t, DRS happens on a vCenter level and HA happens on a host level…. But more things have changed. As of vSphere 4.1 virtual machines will be evenly distributed across hosts to lighten the load on the hostd service and to get quicker power-on results. HA then relies on DRS to redistribute the load later if required. This improvement results in faster restarts of the virtual machines and less stress on the ESX hosts.

So what if you are not using DRS? To put it bluntly, make sure you manual balance your environment to ensure HA doesn’t “overload” a single host… that is the only thing you can do for now. (by the way, all of this is included in the HA and DRS tech deepdive :-))

vSphere 4.1 HA and DRS Technical Deepdive, the book!

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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,