1. High Availability
Module 12

2. Introduction to VMware Virtualization Installing VMware ESX and ESXi
You Are Here
vSphere Environment
Operations
Introduction to VMware Virtualization
Access Control
VMware ESX and ESXi
Resource Monitoring
VMware vCenter Server
Data Protection
Networking
Scalability
Storage
High Availability
Virtual Machines
Patch Management
Installing VMware ESX and ESXi
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3. Importance
Most organizations rely on computer-based services like , databases, and Web-based applications. The failure of any of these services can mean lost productivity and revenue. Configuring highly available, computer-based services is extremely important for an organization to remain competitive in contemporary business environments.
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4. Module Lessons Lesson 1: High Availability
Lesson 2: Managing VMware HA
Lesson 3: FT
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5. Lesson 1: High Availability
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6. Lesson Objectives Describe VMware® solutions for:
High availability
Fault tolerance
Configure a VMware High Availability cluster
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7. High Availability and Fault Tolerance
A highly available system is one that is continuously operational for a desirably long length of time.
A fault-tolerant system is designed so that, in the event of an unplanned outage, a backup component can immediately take over with no loss of service.
Level of availability
Downtime per year
99%
87 hours (3.5 days)
99.9%
8.76 hours
99.99%
52 minutes
99.999%
5 minutes
What level of virtual machine availability is important to you?
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8. VMware Availability and Fault Tolerance Solutions
Availability features in VMware vSphere™:
Storage availability using multipathing
Network availability using network interface card (NIC) teaming
VMware vMotion™ and Storage vMotion
VMware HA
VMware Fault Tolerance (FT)
Support for MSCS clustering
VMware availability product:
VMware vCenter™ Site Recovery Manager:
Decreases planned and unplanned downtime. SRM protects all of your important systems and applications with disaster recovery.
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9. VMware HA, FT, and MSCS Clustering
Level of availability
High availability
Fault tolerance
Amount of downtime
Minimal
Zero
Guest operating systems supported
Works with all supported guest operating systems
Works with Windows operating systems
VMware ESX™/ESXi hardware supported
Works with all supported ESX/ESXi hardware
Widely compatible
Limited to hardware supported by Microsoft
Uses
Use to provide high availability for all your virtual machines.
Use to provide fault tolerance to your critical virtual machines.
Use to provide high availability to application services.
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10. vCenter Server Availability
Make VMware vCenter Server and the components it relies on highly available.
vCenter Server relies on:
vCenter Server database:
Cluster the database. Refer to the specific database documentation.
Active Directory structure:
Set up with multiple redundant servers.
Methods for making vCenter Server available:
Use VMware HA to protect the vCenter Server virtual machine.
Use VMware vCenter Server Heartbeat.
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11. VMware HA
VMware HA:
Provides automatic restart of virtual machines in case of physical host failures
Provides high availability while reducing the need for passive standby hardware and dedicated administrators
Provides support for virtual machine failures with virtual machine monitoring and FT
Is configured, managed, and monitored through vCenter Server
A cluster enabled for VMware HA and DRS can have:
Up to 32 hosts per cluster
Up to 320 virtual machines per host (regardless of the number of hosts/cluster)
Up to 3,000 virtual machines per cluster
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12. VMware HA in Action host host host vCenter Server virtual machine A
LUN 6
LUN 5
LUN 4
LUN 3
LUN 2
LUN 1
virtual machine A
virtual machine B
virtual machine A
virtual machine C
virtual machine E
virtual machine B
virtual machine D
virtual machine F
host
host
host
vCenter Server
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13. Using VMware HA and DRS Together
Using VMware HA and DRS results in fast rebalancing of virtual machines after VMware HA has restarted virtual machines to different hosts.
Reasons why VMware HA might not be able to fail over virtual machines:
VMware HA admission control is disabled and VMware Distributed Power Management is enabled.
Required Virtual Machines to Hosts affinity rule prevents VMware HA from failing over.
Sufficient aggregated resources exist, but they are fragmented across hosts.
In such cases, VMware HA uses DRS to try to adjust the cluster by:
Bringing hosts out of standby mode
Migrating virtual machines to defragment the resources
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14. Detecting a Host Failure
The VMware HA agent monitors the heartbeats between the primary and the secondary hosts to detect host failure.
A heartbeat is sent every second (by default) over the heartbeat network.
On ESXi hosts, the management network is used.
On ESX hosts, the service console network is used.
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15. Host Isolation
If a host in the cluster loses its connection to the heartbeat network but the host continues running, the host is isolated from the cluster.
VMware HA waits 12 seconds before deciding that a host is isolated.
virtual machine
virtual machine
virtual machine
virtual machine
virtual machine
virtual machine
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16. Architecture of a VMware HA Cluster
vCenter
Server
vCenter Server
agent
vCenter Server
agent
vCenter Server
agent
VMware HA
agent
VMware HA
agent
VMware HA
agent
host
host
host
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17. Enabling VMware HA
Enable VMware HA by creating a cluster or modifying a DRS cluster.
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18. Configuring VMware HA Settings
Disable Host Monitoring when performing maintenance activities on the host.
Admission control helps ensure sufficient resources to provide high availability.
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19. Admission Control Policy Choices
Description
Recommended use
Host failures cluster tolerates
Reserves enough resources to tolerate specified number of host failures
When virtual machines have similar CPU and memory reservations
Percentage of cluster resources reserved as failover spare capacity
Reserves specified percentage of total capacity
When virtual machines have highly variable CPU and memory reservations
Specify a failover host
Dedicates a host exclusively for failover service
To accommodate organizational policies that dictate the use of a passive failover host
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20. Configuring Virtual Machine Options
Configure options at the cluster level or per virtual machine.
VM restart priority determines relative order in which virtual machines are restarted after a host failure.
Host Isolation response determines what happens when a host loses the management (or service console) network but continues running.
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21. Configuring Virtual Machine Monitoring
Restart a virtual machine if its VMware Tools heartbeat or VMware Tools application heartbeats are not received.
Determine how quickly failures are detected.
Set monitoring sensitivity for individual virtual machines.
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22. Monitoring Cluster Status
The Cluster Operational Status window displays the current VMware HA operational status, including the specific status and errors for each primary and secondary host in the cluster.
cluster’s Summary tab
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23. Lab 23 In this lab, you will demonstrate VMware HA functionality.
Create a cluster enabled for VMware HA.
Test VMware HA functionality.
Prepare for the next lab.
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24. Lesson Summary Describe VMware solutions for:
High availability
Fault tolerance
Configure a VMware HA cluster
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25. Lesson 2: Managing VMware HA
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26. Lesson Objectives Configure VMware HA advanced options
Configure redundant heartbeat networks
Configure redundant isolation test addresses
View the status of cluster operations
Follow best practices when configuring VMware HA clusters
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27. Planning Resources for a VMware HA/DRS Cluster
How much CPU and memory resources is the cluster using now?
How much reserved capacity remains?
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28. Importance of Redundant Heartbeat Networks
In a VMware HA cluster, heartbeats are:
Sent between the primary and the secondary hosts
Used to determine if a primary host failed
Sent over the heartbeat network
The heartbeat network is:
On ESXi hosts, the management network
On ESX hosts, the service console network
Redundant heartbeat networks:
Allow for the reliable detection of failures
Help prevent isolation conditions from occurring
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29. Redundancy Using NIC Teaming
You can use NIC teaming to create a redundant heartbeat network on ESX/ESXi hosts.
NIC teaming on an ESXi host
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30. Redundancy Using Additional Networks
You can also create redundancy by configuring more heartbeat networks:
On ESXi hosts, add one or more VMkernel networks marked for management traffic.
On ESX hosts, add one or more service console networks.
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31. How Hosts Test for Isolation
An isolation address is an IP address that is pinged to determine whether an ESX/ESXi host is isolated from the network.
Hosts in the VMware HA cluster test themselves for isolation by pinging the isolation address.
By default, ESXi hosts ping the VMkernel gateway IP address.
By default, ESX hosts ping the service console default gateway IP address.
As a best practice, configure redundant isolation addresses.
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32. Configuring Isolation Addresses
To configure more isolation addresses, set das.isolationaddress#.
When more isolation addresses are configured, increase the value of das.failuredetectiontime.
To prevent use of the default isolation address, set das.usedefaultisolationaddress.
Ensure that your isolation addresses are reliable IP addresses.
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33. Network Configuration and Maintenance
Before changing the networking configuration on the ESX/ESXi hosts (adding port groups, removing vSwitches):
Deselect Enable Host Monitoring.
Place the host in maintenance mode.
These steps prevent unwanted attempts to fail over virtual machines.
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34. Lab 24 In this lab, you will modify slot sizes and admission control.
Use the Resource Allocation tab to determine resource use.
Manage VMware HA slot size.
Configure a VMware HA cluster with strict admission control.
Configure a VMware HA cluster with flexible admission control.
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35. Lab 25 (Optional)
Do not perform this lab unless agreed to by your instructor.
In this lab, you will configure VMware HA network redundancy.
Enable technical support mode on an ESXi host.
Test default VMware HA failure detection time.
Modify and test VMware HA failure detection time.
Configure management network redundancy.
Configure VMware HA host isolation response.
Test network isolation functionality.
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36. Lesson Summary Configure VMware HA advanced options
Configure redundant heartbeat networks
Configure redundant isolation test addresses
View the status of cluster operations
Follow best practices when configuring VMware HA clusters
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37. Lesson 3: FT
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38. Lesson Objectives Compare VMware HA, FT, and MSCS clustering
List FT requirements and limitations
Describe FT operation
Configure, monitor, and test a fault-tolerant virtual machine
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39. What Is FT?
FT:
Provides a higher level of business continuity than VMware HA
Provides zero downtime and zero data loss for applications
FT can be used for:
Any application that needs to be available at all times
Custom applications that have no other way of doing clustering
Cases where high availability might be provided through Microsoft Cluster Service but MSCS is too complicated to configure and maintain
FT can be used with DRS:
Fault-tolerant virtual machines benefit from better initial placement and are included in the cluster’s load-balancing calculations.
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40. FT in Action vLockstep technology vLockstep technology
new primary VM
primary VM
secondary VM
new secondary VM
FT provides zero-downtime, zero-data-loss protection to virtual machines in a VMware HA cluster.
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41. vSphere configuration
Requirements for FT
Component
FT requirement
vSphere configuration
Host certificate checking enabled on all hosts
Hardware certified for FT
Storage
Virtual machines stored on shared storage
Virtual machines provisioned with thick virtual disks
Virtual machines not stored on physical RDMs
Networking
Minimum of two gigabit NICs, one for vMotion and one for FT logging. Three or more NICs are recommended.
Processor
Uniprocessor virtual machines
Hosts processors from FT-compatible processor group
Virtual machines running a supported guest operating system
Host BIOS
Hardware Virtualization enabled
Same instruction set extension configuration applied to all hosts
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42. single copy of disks on shared storage
How FT Works
primary
virtual machine
secondary
virtual machine
VMkernel
VMM
VMM
VMkernel
Log update?
Log read?
record logs
log buffer
log buffer
Heartbeat?
read/write
read
single copy of disks on shared storage
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43. FT Guidelines Check the requirements and limitations of FT.
Ensure enough ESX/ESXi hosts for fault-tolerant virtual machines:
No more than four fault-tolerant virtual machines (primaries or secondaries) on any single host
Store ISOs on shared storage for continuous access:
Especially if used for important operations
Disable BIOS-based power management:
Prevents the secondary virtual machine from having insufficient CPU resources
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44. Enabling FT Logging on a Host
For each ESX/ESXi host in the cluster, create a VMkernel networking interface to use for FT logging.
enabling FT logging on a vNetwork standard switch
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45. Enabling FT on a Virtual Machine
virtual machine’s Summary tab
After you turn on FT, the Summary tab on the primary virtual machine reports FT information.
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46. Managing Virtual Machines Enabled for FT
Use the commands from the shortcut menu to test and manage the virtual machine enabled for FT.
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47. Lab 26 and eLearning Activity
Do lab 26 if you are using a lab environment that supports FT.
In this lab, you will configure FT for a virtual machine and verify that FT works.
Enable FT logging.
Activate FT.
Test FT.
Disable FT.
Otherwise, perform the eLearning activity:
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48. Lesson Summary Compare VMware HA, FT, and MSCS clustering
List FT requirements and limitations
Describe FT operation
Configure, monitor, and test a fault-tolerant virtual machine
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49. Key Points
A good practice is to enable both DRS and VMware HA in a cluster.
Implement redundant heartbeat networks either with NIC teaming or by creating additional heartbeat networks.
FT provides zero downtime for applications that need to be available at all times.
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