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Chapter 11. High Availability > Frequently Asked Questions

Frequently Asked Questions

  • Does high availability prevent all downtime?
  • No. While high availability can prevent downtime in many circumstances, in some cases it doesn't prevent downtime rather it reduces recovery time by bringing impacted machines online faster.
  • Do I have to use the same hardware for all hosts in a high availability cluster?
  • While you do not have to have the exact same hardware, it is highly recommended. In particular many vendors require the same processor type for effective high availability.
  • Is resource over commitment a concern with high availability?
  • Yes. Because high availability functionality generally entails that some portion of the production capacity and resources have failed and are no longer accessible (in essence you are operating at reduced capacity to begin with), if you do not have spare capacity to allow for the high availability functionality to bring virtual machines online on alternate hosts, high availability operations may not be able to occur. You want to ensure that, at a minimum, you provide N+1 capacity to eliminate resource over commitment concerns.


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