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Objective 2.3 – Build Availability Requirements into the Logical Design


  • Understand what logical availability services are provided by VMware solutions.
    • VMware High Availability – minimizes downtime by restarting virtual machine on remain hosts in case of hardware failure
    • VMware Fault Tolerance – Provides continuous availability in case of hardware failure by running a copy of the virtual machine in parallel but any OS or application failure would be replicated.
  • Identify and differentiate infrastructure qualities (Availability, Manageability, Performance, Recoverability, Security)
    • Availability – ability to access resources when needed, this is achieved using redundancy usually defined in the SLA as up time
    • Manageability – is it Easy to deploy, Easy to administer, Easy to upgrade
    • Performance – Measured usually by Throughput, latency or transaction time
    • Recoverability – the ability to return the system to a working state after a failure
    • Security – Correct people have access, firewalls need to be opened etc
  • Describe the concept of redundancy and the risks associated with single points of failure.

Redundancy is basically having a backup in case something was to fail, network redundancy would be have 2 physically separate NICs attached to physically separate switches, this was if a NIC was to die network would still be available through the “redundant” NIC remaining, if a switch was to die we would still have network through the “redundant” switch.

Having a single point of failure means if that single point was to fail the service being provided would be down.

  • Differentiate Business Continuity and Disaster Recovery concepts.

Business continuity is a proactive action focused on avoiding or mitigating the impacts of risks before they happen.

Disaster recover is focused on how to return services after an outage or failure has occurred which is a reactive action

Skills and Abilities

  • Determine availability component of service level agreements (SLAs) and service level management processes.

For example if your SLA specified that a particular Service can have a VM failure of 0 then the choice would be VMware FT but this then incurs a risk that the VM can only run on a single CPU. But if the SLA said there can only be a 5 minute outage a month then VMware HA would most likely have that covered.

  • Explain availability solutions for a logical design based on customer requirements.

Fault Tolerance would be displayed like so for a logical design


  • Define an availability plan, including maintenance processes.

This will depend on what type of failure your defining, for Host Upgrades make a plan to vMotion virtual machines off to other hosts ensuring there is enough resources available, update the host, then move VMs back. Or for VM maintenance define a process of snapshotting the VM revert back if there is a failure, remove if its a success. etc

  • Prioritize each service in the Service Catalog according to availability requirements.

Obviously what i would call category A applications would require a priority when returning services, This can be done through restart priority in VMware HA, set the more important applications or services to have a high restart priority.

  • Balance availability requirements with other infrastructure qualities

Infrastructure Qualities are Availability, Manageability, Performance, Recoverability and Security.

Using VMware’s core technologies such at HA, DRS, FT along with its inbuilt support for redundant network and storage interfaces, it balances well across all the qualities.

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