1. VMware vCenter Server High Availability
Product Support Engineering
VMware Confidential

2. Module 2 Lessons Lesson 1 – vCenter Server High Availability
Lesson 2 – Distributed Resource Scheduler
Lesson 3 – Fault Tolerance Virtual Machines
Lesson 4 – Enhanced vMotion Compatibility
Lesson 5 – DPM - IPMI
Lesson 6 – vApps
Lesson 7 – Host Profiles
Lesson 8 – Reliability, Availability, Serviceability ( RAS )
Lesson 9 – Web Access
Lesson 10 – vCenter Update Manager
Lesson 11 – Guided Consolidation
Lesson 12 – Health Status
Agenda Overview
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3. Module 2-1 Lessons Lesson 1 – Overview of High Availability
Lesson 2 – VMware HA Clusters
Lesson 3 – Creating HA Clusters
Lesson 4 – Monitoring HA Clusters
Lesson 5 – HA Clusters Best Practices
Lesson 6 – Troubleshooting VMware HA
Lesson 7 – Customizing VMware HA
Agenda Overview
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4. VMware High Availability
This section provides information about using solutions that provide business continuity, including how to establish VMware High Availability (HA) and VMware Fault Tolerance.
VMware Infrastructure provides multiple ways to ensure that the information and services in your business infrastructure are consistently available.
VMware offerings can be placed into the following categories:
High availability through reduced (planned and unplanned) downtime. Solutions for this include Fault Tolerance and VMware High Availability (HA).
Data protection including non disruptive backup and restore processes. A solution for this is VMware Consolidated Backup (VCB).
Disaster recovery with hardware independent recovery. A solution for this is Site Recovery Manager (SRM).
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5. High Availability Solutions
Unplanned downtime
VMware Infrastructure builds fault tolerance capabilities into datacenter infrastructure.
These features can be easily configured, thus reducing the cost and complexity of providing higher availability.
Key fault-tolerance capabilities built into VMware Infrastructure include:
Network interface (NIC) teaming to provide tolerance of individual network card failures
Storage multipathing to tolerate storage path failures
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6. High Availability Solutions
VMware High Availability and VMware Fault Tolerance, implemented through VMware Infrastructure, offer simple, cost effective solutions that help mitigate situations that could otherwise make data or services unavailable to users.
VMware HA - Checks that ESX/ESXi hosts are functioning. If an ESX/ESXi host fails, another ESX/ESXi host restarts any virtual machines that were running on the server that failed.
VMware Fault Tolerance (FT) - Checks that individual virtual machines are functioning and deals with failures without any interruption in service. VMware FT creates hidden duplicate copies of running virtual machines so if a virtual machine fails due to hardware or software failures, the duplicate virtual machine can immediately replace the one that was lost.
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7. High Availability Solutions
High availability and fault tolerance are different from other business continuity offerings in that the solution:
Exists within a single datacenter. Other solutions exist across physical locations.
Uses shared storage for holding the machines' data. Other solutions use multiple copies of the data, which are regularly replicated.
Fault tolerance addresses a number of common problematic situations
Fault Tolerance will be discussed in Module 2-3.
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8. Providing High Availability with VMware HA
When using VMware HA, a set of ESX/ESXi hosts is combined into a cluster with a shared pool of resources.
vCenter Server monitors all hosts in the cluster. If one of the hosts fails, each associated virtual machine is promptly restarted on a different host.
Using VMware HA has a number of advantages:
Minimal setup — The New Cluster Wizard is used for initial setup.
Reduced hardware cost and setup — The virtual machine acts as a portable container for the applications and the virtual machine can be moved among hosts.
Increased application availability — Any application running inside a virtual machine has access to increased availability.
Full Distributed Resource Scheduler (DRS) integration — If a host has failed and virtual machines have been restarted on other hosts DRS can provide migration recommendations or migrate virtual machines for balanced resource allocation
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9. Virtual Machine Resource Requirements and VMware HA
When establishing a VMware HA cluster, decide how to make the best use of resources available on hosts while providing a high level of availability for virtual machines.
Consider the following factors:
Each host has some amount of memory and CPU that it can make available for use by virtual machines.
Each virtual machine must be guaranteed its CPU and memory reservation requirements.
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10. Understanding the Resource Allocation Tab in Clusters
If the host being used to start a virtual machines is in a cluster, you can view information about reserved resources on the Resource Allocation tab for that cluster.
The information for the CPU and Memory reservations indicates that reservations have been made
Summary reservation information displays information about reservations on the cluster root, where all reservations occurred.
Individual virtual machines do not actually have any reservations.
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11. VMware HA Cluster Prerequisites
This section describes the prerequisites for establishing VMware HA clusters.
A number of conditions must be established for VMware HA to be used.
All virtual machines and their configuration files must reside on shared storage (such as a SAN)
Hosts must also be configured to have access to the same virtual machine network.
Each host in a VMware HA cluster must have a host name assigned and a static IP address.
VMware recommends redundant Service Console and VMkernel networking
NOTE After you have added a NIC to a host in your VMware HA cluster, you must reconfigure VMware HA on that host.
There has been no change from ESX 3-4 on the requirements for HA
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12. A note on VMware HA ‘slot’ Calculation
Slot calculation is still done by the vCenter HA service.
It gives the HA service the capacity of the cluster as a whole
For Virtual Center 2.x the VM with maximum resource consumption was the one chosen as the basis of the slot calculation.
This poised a problem if there was only one heavily resourced Virtual Machine and the other VM’s did not use so much resources.
You would get an unfair calculation of remaining resources.
This has been changed for vCenter 4.
The slot size is shown in the UI.
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13. A note on VMware HA ‘slot’ Calculation
When you use the Host failures cluster tolerates option, it is most effective if all virtual machines have a similar CPU and memory requirement.
If you have highly variable configurations, consider using the Percentage of cluster resources reserved as failover spare capacity option.
When tolerating a specific number of host failures, VMware HA plans for a worst-case scenario by considering all powered-on virtual machines in a cluster and finding the maximum memory and CPU reservations.
These maximums are the basis for what is called a slot, which is a logical representation of the largest virtual machine in the cluster.
If no reservations are set on a virtual machine, default requirements of 256MB and 256MHz are assigned.
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14. A note on VMware HA ‘slot’ Calculation
VMware HA determines how many slots are available in each ESX/ESXi host based on the host’s CPU and memory capacity.
VMware HA then determines how many ESX/ESXi hosts could fail with the cluster still having at least as many slots as powered on virtual machines.
When you use the Percentage of cluster resources reserved as failover spare capacity option, each time a request is made to power on a virtual machine, admission control determines the amount of resources the virtual machine needs and how much uncommitted resources remain on cluster resources for failovers.
If sufficient resources are available, the virtual machine is powered on. This process does not guarantee maintaining a level of service if a number of hosts fail, but it is a more flexible and less conservative approach to assessing whether or not to power on machines.
This policy does not use slots. It uses the actual reservations of the virtual machines. If a virtual machine does not have reservations, meaning that the reservation is 0, a default of 256MB and 256MHz is applied. This is controlled by the same HA advanced options used for the failover level policy.
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15. Monitoring Availability
You can monitor changes in your high-availability deployment using events and alarms
Use the functionality included in Alarms and Actions to determine what actions are taken when VMware HA events occur.
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16. Creating a VMware HA Cluster
Clusters enable a collection of ESX/ESXi hosts to work together.
This provides higher levels of availability for virtual machines
You can create a new cluster using the Cluster Creation Wizard
Begin: Start by right clicking and adding a new cluster (note there are clusters already created)
Click: You name the cluster and check the checkbox for HA
Click: You then select your addmission control.
- You’ll note at the top the Host monitoring checkbox that allows you to do network maintenance
- You’ll note at the bottom there is a Percentage of cluster resources that can be reserved for failover (more on that later).
Click: Restart priortiy and isolation mode (nothing new)
Click: VM monitoring or individual VM restarts are now supported in vCenter. The VM is restarted if the heartbeat is lost.
Click: Swap space confirmation (nothing new)
Click: click finish and HA will setup
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17. Creating a New VMware HA Cluster
Some key settings include:
Admission Control specifies the kind of policy to enforce to ensure that there are enough resources to perform a failover in the case of a host failure. If enabled, admission control prevents certain operations on virtual machines (such as powering them on) if doing so would violate the policy.
Monitoring Sensitivity, determines the duration VMware HA waits between heartbeats before restarting virtual machines that were hosted on the ESX/ESXi host from which a heartbeat has not been received.
Default Cluster Settings determine how quickly virtual machines are restarted and what action to take if a host becomes isolated.
Nothing new
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18. Cluster Features
The first panel in the New Cluster wizard allows you to specify basic options for the cluster, including:
Name — Specifies the name of the cluster. This name appears in the VI Client inventory panel. You must specify a name to continue with cluster creation.
Turn On VMware HA — If this box is selected, virtual machines on are restarted on different host in a cluster if one of the cluster's hosts fails.
Turn On VMware DRS — If this box is selected, DRS uses load distribution information for initial placement and load balancing recommendations or to place and migrate virtual machines automatically.
In this panel you can specify the name and choose one or both cluster features. You can change any of these cluster features at a later time.
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19. Host Monitoring Status and Admission Control
Configure host monitoring and Virtual Machine admission control.
High Availability services check if ESX/ESXi hosts and virtual machines are available
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20. Admission Control
Admission control helps ensure that sufficient resources remain to provide high availability, even after some number of concurrent host failures.
Some resources in a cluster are reserved until they are needed for recovery from failure.
To prevent too many virtual machines from starting, which would leave too few resources available for failover, VMware HA uses admission control.
Nothing new, what is more important Uptime or resource fairness. This is the only area where the VMkernel will ignore reservations if you select the bottom option. More on next slide.
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21. Admission Control
You can enable or disable admission control by selecting the following options:
Prevent VMs from being powered on if they violate availability constraints — Enforcing availability constraints preserves failover capacity. If this option is selected (the default), the following operations are also not allowed if they would violate admission control:
Reverting a powered off virtual machine to a powered on snapshot
Migrating a virtual machine into the cluster
Reconfiguring a virtual machine to increase its CPU or memory reservation
Allow VMs to be powered on even if they violate availability constraints
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22. Admission Control Policy
VMware HA provides options for what policy is enforced if admission control is enabled.
Host failures cluster tolerates – VMware HA reserves a certain amount of resources across a set of hosts. These reserved resources are sufficient to sustain performance even if the specified number of hosts fail.
Percentage of cluster resources reserved as failover spare capacity – VMware HA reserves a certain percentage of aggregate resources in the cluster to accommodate failures.
Specify a failover host – VMware HA reserves a specific host to accommodate failures. This is a more static solution, where a single host is designated as the host that will be the target for virtual machines if one of the other hosts fails.
Because this setup can only tolorate one host failure you cannot specify a specific host. You can enter an advanced option to specify what host to failover to (later in the module).
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23. Tolerate Some Number of Host Failures
You can configure VMware HA to tolerate a specified number of host failures.
When using the “Host failures cluster tolerates” option, it is most effective if all virtual machines have a similar CPU and memory requirement.
If you have highly variable configurations, consider using the “Percentage of cluster resources reserved as failover spare capacity” option
Each host has some amount of memory and CPU that it can make available for use by virtual machines.
Each virtual machine must be guaranteed its CPU and memory reservation requirements.
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24. Tolerate Some Number of Host Failures
Does HA restart VM’s on multiple hosts after a failure or does it function the same as 3.x where the host with the most unreserved capacity is chosen to restart the VM’s on and DRS will load balance those VM’s.
-Pending PSE response.
- Assume that it functions the same as ESX 3.x and that this picture is inaccurate on the functionality.
Examples
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25. Tolerate Some Number of Host Failures
Examples
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26. Reserve a Percentage of Cluster Resources
You can configure VMware HA to reserve a specific percentage of cluster resources for recovery from host failures
When using the “Percentage of cluster resources reserved as failover spare capacity” option,
Each time a request is made to power on a virtual machine, admission control determines the amount of resources the virtual machine would need and how much uncommitted resources remain on cluster resources for failovers
This policy does not use slots, but rather it uses the actual reservations of the virtual machines.
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27. Specify a Failover Host
You can configure VMware HA to reserve a specific host as failover capacity.
When using the Specify a failover host option,
If one host fails, first attempts are made to restart the virtual machines on the reserved host, but if this is not possible for some reason such as insufficient resources or that the reserved host has failed, attempts are made to restart virtual machines on any available host in the cluster
This option does not guarantee a level of availability.
It establishes a spare host to use in case of failover
If a failover host is specified, HA admission control prevents users from powering on a virtual machine on the failover host or VMotioning virtual machines to the failover host
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28. Default Cluster Settings and Virtual Machine Overrides
Default virtual machine settings controls
The order in which virtual machines are restarted
How VMware HA responds if hosts lose network connectivity with other hosts
Default settings apply to all virtual machines in this cluster in the case of a host failure or isolation, though exceptions can be configured for each virtual machine
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29. VM Restart Priority
VM restart priority determines the relative order in which virtual machines are restarted after a host failure.
Assign higher restart priority to the virtual machines that host the most important services.
For example, in the case of a multi-tier application you might opt to rank assignments according to functions hosted on the virtual machines:
High: Database servers that will provide data for applications.
Medium: Application servers that consume data in the database and provide results on web pages.
Low: Web servers that receive user requests, pass queries to application servers, and return results to users.
This is done alphabetically still
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30. Host Isolation Response
Determines what happens when a host in a VMware HA cluster loses its service console networks (or Vmkernel networks, in ESXi) connection but continues running.
Values are: Leave VM powered on (the default), Power off VM, and Shut down VM.
When a host in a HA cluster loses its console network (or VMkernel network, in ESXi) connectivity, the host is isolated from other hosts in the cluster.
Virtual Machine Settings
You can override the default settings established for the cluster. For each virtual machine, you can establish individual settings for Restart Priority and Isolation Response.
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31. Virtual Machine Monitoring Sensitivity
The degree to which VMware HA is sensitive to virtual machine failures can be configured to different levels.
If you select Enable VM Monitoring, VMware Tools will evaluate whether each virtual machine in the cluster is running by checking for regular heartbeats from the GOS.
In such a case, the VM monitoring service determines that the virtual machine has failed and the virtual machine is rebooted to restore service
Click on the Custom box to configure advanced features for Monitoring Sensitivity
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32. Best Practices for Configuring VMware HA Clusters
Networking Best Practices
If your switches support the PortFast (or an equivalent) setting, enable it on the physical network switches that connect servers.
This helps to prevent a host from incorrectly determining that a network is isolated during the execution of lengthy spanning-tree algorithms
On ESX hosts, HA automatically opens the firewall ports that are needed for it to function. The following ports are opened:
Incoming port: TCP/UDP
Outgoing port: TCP/UDP
Why do we disable portfast on the physical switch that are connected to the vSwitch?
a: vswitches do not connect to other vSwitches via ISL.
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33. Best Practices for Configuring VMware HA Clusters
For better heartbeat reliability, configure end-to-end dual network paths between servers for service console or VMKernel networking.
Disable VMware HA (clear the Enable VMware HA checkbox in the Settings dialog box for the cluster) when you perform any networking maintenance that might disable all heartbeat paths between hosts.
While DNS is not required, you may choose to use DNS for name resolution rather than the error-prone method of manually editing the local /etc/hosts file on ESX/ESXi hosts. If you do edit /etc/hosts, you must include both long and short names.
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34. Best Practices for Configuring VMware HA Clusters
Use consistent port names on VLANs for public networks.
Port group names are used to reconfigure access to the network by virtual machines.
If you use inconsistent names between the original server and the failover server, virtual machines are disconnected from their networks after failover.
Use valid virtual machine network labels on all servers in a VMware HA cluster.
Virtual machines use these labels to reestablish network connectivity upon restart
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35. Best Practices for Configuring VMware HA Clusters
Selection of Networks
The networks that HA will use by defaults is:
ESX: all Service Console Networks
ESXi: All VMKernel networks, *except* the VMotion network, unless there is only one network and it is a VMotion network
By default, the network isolation address is the default gateway , so it is a best practice to add a das.isolationaddress[...] for each network
HA to select the default networks you can use the advanced option das.allowNetwork[...] and HA will use only networks whose port group names match.
ESXi by default uses all VMKernel networks, except the VMotion Network unless there is only one network defined. Use das.AllowVmotionNetworks to override this default behavior. Also, you can use das.allowNetwork[...] to specify the networks that will be used for HA.
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36. Clusters with both ESX and ESXi hosts
In mixed ESX and ESXi clusters, using the das.allowNetwork[...] advanced options may be necessary to ensure compatible networks are selected for hosts.
HA configuration enforces that all hosts in the cluster have compatible networks.
The first node added to the cluster dictates the networks that all subsequent hosts must have for them to be allowed into the cluster
Networks are deemed compatible if the IP address and subnet mask combine to result in a network that matches another host's
Use das.allowNetwork[...] advanced options to control which networks are to be used to ensure compatibility between all hosts in the cluster
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37. Setting Up Networking Redundancy
Networking redundancy between cluster nodes is important for VMware HA reliability.
Redundant service console networking on ESX4 (or VMkernel networking on ESXi) allows the reliable detection of failures and prevents isolation conditions from occurring.
NIC Teaming
Using a team of two NICs connected to separate physical switches improves the reliability of a service console (or, in ESXi, VMkernel) network.
To configure a NIC team for the service console, configure the vNICs in vSwitch configuration for Active or Standby configuration. The recommended parameter settings for the vNICs are:
Default load balancing = route based on originating port ID
Failback = No
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38. Secondary Service Console Network
You can create a secondary service console (or VMkernel port for ESXi), which is attached to a separate virtual switch
The primary service console is used for network and management purposes.
With a secondary service console network created, VMware HA sends heartbeats over both the primary and secondary service consoles.
When you set up service console redundancy, you must specify an additional isolation response address (das.isolationaddress2) for the service console networks
When you specify a secondary isolation address, you should increase the das.failuredetectiontime setting to milliseconds or greater
Adding a secondary service console network to the VMotion vswitch. A virtual switch can be shared between VMotion networks and a secondary service console network.
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39. Other VMware HA Cluster Considerations
Use larger groups of homogeneous servers to allow higher levels of utilization across an VMware HA-enabled cluster (on average).
More nodes per cluster can tolerate multiple host failures while still guaranteeing failover capacities.
The failover level policy used in admission control heuristics is conservatively weighted, so that virtual machines on large servers can fail over to smaller servers.
;-)
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40. Modifying Cluster Settings
You can modify cluster settings using the Edit Cluster Settings dialog box
To complete this task, you must use an account with cluster administrator privileges.
Right-click the cluster in the VI Client inventory panel and click Edit Settings.
In the left pane of the cluster Settings dialog box, click the set of options you want to modify.
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41. Viewing Information about VMware HA Clusters
You can view current settings for a cluster
The cluster Summary page displays summary information for the cluster.
Note this screenshot is outdates: There is an Advanced Link in the VMware HA portion that will show you the slot calculation.
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42. How VMware HA Works
VMware HA designates hosts for particular roles and responds to problems as they arise.
In a VMware HA deployment, a set of ESX/ESXi hosts is combined into a cluster with a shared pool of resources.
Hosts in the cluster are monitored and if one of the hosts fails, virtual machines that were running on the failed host are restarted on a different host.
VMware HA can be used in conjunction with VMware Fault Tolerance to provide preservation of run-time state and even shorter application downtime.
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43. Using VMware HA with Admission Control
Admission control helps ensure that VMware HA performs as expected.
When you enable a cluster for VMware HA, you can specify how much host capacity to reserve so that the cluster through one of the following strategies:
Is prepared to tolerate some number of host failures.
Reserves some percentage of total capacity.
Specifies a particular host exclusively for failover purposes.
If a host fails, VMware HA attempts to restart virtual machines on one of the remaining hosts.
By default, you cannot power on a virtual machine if doing so violates the admission control policy.
This is the same functionality of ESX 3
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44. Primary and Secondary Hosts
Some hosts in a VMware HA cluster are designated as primary hosts.
They maintain information about the cluster such as membership.
The first five hosts in the cluster are designated primary hosts, and all subsequent hosts are designated secondary hosts.
When you add a host to a VMware HA cluster, that host communicates with an existing primary host in the same cluster to complete its configuration
When a primary host becomes unavailable or is removed from the cluster
VMware HA promotes one of the secondary hosts to primary status.
Primary hosts help provide redundancy by replicating the cluster's configuration information and virtual machine states and are used to initiate failover actions
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45. VMware HA Clusters and Maintenance Mode
Put a host in maintenance mode in preparation for completing administrative tasks that would otherwise cause unwanted HA responses.
Putting a host into maintenance mode effectively disables the HA service.
You cannot power on a virtual machine on a host that is in maintenance mode.
VMware HA does not fail over any virtual machines to a host that is in maintenance mode
When a host exits maintenance mode, the VMware HA service is reenabled on that host, so it becomes available for failover again
If the host is in a cluster, when it enters maintenance mode the user is given the option to evacuate powered-off virtual machines
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46. VMware HA Clusters and Disconnected Hosts
Users may initiate state changes, such as during network maintenance.
ESX/ESXi host in a cluster may no longer be able to communicate with other hosts in a cluster
That host becomes disconnected
The unresponsive host continues to function, but its state is unknown
When a host is disconnected, VMware HA cannot use it as a guaranteed failover target.
VMware HA does not consider disconnected hosts when making calculations related to admission control.
When the host becomes reconnected, the host becomes available for failover again
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47. VMware HA Clusters and Disconnected Hosts
The difference between a disconnected host and a host that is not responding is that:
A disconnected host has been explicitly disconnected by the user. As part of disconnecting a host, VMware HA is disabled on that host. The virtual machines on that host are not failed over and not considered when the current failover level is computed.
If a host is not responding, no other hosts receive heartbeats from it. This might happen, for example, because of a network problem or because the host failed.
Disconnected and unresponsive hosts are not included in computations of the current failover level, but any virtual machines running on an unresponsive host will be failed over if the host fails.
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48. VMware HA Clusters and Host Network Isolation
Network isolation occurs when a host is still running, but it can no longer communicate with other hosts in the cluster.
Hosts are determined to have failed after the time limit between heartbeats has elapsed and no heartbeat has been received.
The default heartbeat monitoring sensitivity detects failures after 15 seconds have elapsed.
The host declares itself as isolated from the network after it has lost network connectivity for more than 12 seconds and is unable to ping its isolation address or addresses (default gateway).
If the isolated host has SAN access, it retains the disk lock on the virtual machine files, and any attempts to fail over the virtual machine to another host would fail.
The virtual machine continues to run on the isolated host
VMFS disk locking prevents simultaneous write operations to the virtual machine disk files and potential corruption
Same as ESX 3.x
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49. VMware HA Clusters and Host Network Isolation
If the network connection is restored before 12 seconds have elapsed, other hosts in the cluster do not treat this as a host failure, but rather as a transient issue that has been resolved.
If the network connection is not restored for 15 seconds or longer, the other hosts in the cluster treat the host as failed and attempt to fail over the virtual machines on that host.
Same as 3.x
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50. Setting Up Virtual Machine-Level Overrides
You can configure overrides for individual virtual machines so that their behavior differs from cluster defaults.
Virtual machine-level overrides are useful for machines that are used for special tasks.
For example, Virtual machines that are especially important, such as those that provide infrastructure services like DNS or DHCP, may need to be powered on before other virtual machines in the cluster.
Set the priority properly based on the function of the VM. Same as ESX 3.x
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51. Monitoring Individual Virtual Machines
You can specify behavior for individual virtual machines for:
VM Restart Priority — Indicates relative priority for restarting the virtual machine in case of host failure.
Host Isolation Response — Specifies what the ESX/ESXi host that has lost connection with its cluster should do with running virtual machines.
Monitoring Sensitivity — Specifies how quickly failures are detected. Settings can be changes so certain virtual machines are more or less aggressively monitored. Specific custom values can also be set using advanced options.
When you add a host to a cluster, all virtual machines in the cluster default to the cluster’s default VM restart priority (Medium, if unspecified), default host isolation response (Leave Powered Off, if unspecified), and default monitoring sensitivity (High, if unspecified).
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52. Customize VMware HA Behavior for Individual VMs
You can select specific behavior for each virtual machine.
Edit the Cluster Settings
Choose VM Monitoring under VMware HA.
For each virtual machine in the Virtual Machine Settings pane, select a VM Monitoring setting to customize its settings.
Choose VM Options under VMware HA.
For each virtual machine, select from the VM Restart Priority or Host Isolation Response menu to customize its settings.
Same as ESX 3.x
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53. Cluster Validity
Cluster validity is based on whether or not there are sufficient resources for hosts to continue to provide the level of service expected for virtual machines.
You can review the validity of a cluster using the VI Client,
You can review the validity of a cluster using the VI Client, which indicates whether a cluster is valid (green) or invalid (red).
A valid cluster is one in which the admission control policy is not violated.
A cluster is valid unless something happens that makes it over-committed or invalid.
If a cluster becomes invalid, a message is displayed in the Summary page indicating the issue.
Some of the ways cluster can become invalid include:
A host failure prevented the required level of spare capacity to be preserved
All the primary hosts in the cluster are not responding.
Same as ESX 3.x
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54. Cluster Validity
A cluster enabled for VMware HA becomes red when the number of virtual machines powered on exceeds the failover requirements
The current failover capacity is less than configured failover capacity
If admission control is disabled, clusters do not become red, regardless of whether the hosts can guarantee failover.
Inadequate failover capacity can happen if VMware HA is set up for two-host failure in a four-host cluster and one host fails.
The remaining three hosts may no longer be able to satisfy a two-host failure.
Note that DRS behavior is not affected if a cluster is red because of a VMware HA issue.
Same as ESX 3.x
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55. Using VMware HA and DRS Together
VMware HA will perform more efficiently when used in conjunction with DRS.
Using VMware HA and DRS together combines automatic failover with load balancing.
In a cluster using DRS and VMware HA with admission control turned on, virtual machines might not be evacuated from hosts entering maintenance mode.
This is because of the resources reserved to maintain the failover level.
You must manually migrate the virtual machines off of the hosts using VMotion
Same as ESX 3.x
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56. Troubleshooting VMware HA
If no hosts in a cluster are responding, when you attempt to add a new host, VMware HA configuration fails because the new host cannot communicate with any of the primary hosts.
Disconnect all hosts that are not responding before adding the new host.
After disconnecting all other hosts and adding a new host, that host becomes the first primary host.
When other hosts become available again, their VMware HA service is reconfigured and they then become primary or secondary hosts depending on the existing number of primary hosts.
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57. Customizing VMware HA
After you have established a cluster, you may need to modify settings. There are specific attributes that affect how VMware HA behaves
Note the das.defaultfailoverhost can be used in the advanced options if the display is greyed out like we seen in the earlier slide
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58. Customizing VMware HA VI4 - Mod 2-1 - Slide
Screenshot coming up showing where to enter these in the UI.
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59. Customizing VMware HA
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60. Set Advanced VMware HA Options
To precisely customize VMware HA behavior, set advanced VMware HA options.
Prerequisites
You must have a VMware HA cluster for which to modify settings.
To modify advanced VMware HA settings, you must have cluster administrator privileges.
In the cluster’s Settings dialog box, select VMware HA.
Click the Advanced Options button to open the dialog box.
Enter each advanced attribute you want to change in a text box
Click OK.
BEGIN: You have to click the advanced options in order to enter these values
CLICK: this is where you enter your advanced HA values.
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61. Lesson 2-1 Summary Learn how to Create a HA Cluster
Learn how to Monitor a HA Cluster
Learn how to modify HA Cluster Settings
Learn how to troubleshoot HA Clusters
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62. Lab – VMware High Availability
Lab 1 Part 1 - Creating a vCenter High Availability (HA) Cluster
Lab 1 Part 2 – Adding Hosts to High Availability (HA) Cluster
Lab 1 Part 3 – Viewing High Availability (HA) Cluster Settings
Lab 1 Part 4 – Modifying High Availability (HA) Cluster Settings
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