High Availability

High Availability Module 12

Module 2-2

Operations

You Are Here

VMware vSphere 4.1: Install, Configure, Manage – Revision A

vSphere Environment

High Availability

Introduction to VMware Virtualization

VMware ESX and ESXi

VMware vCenter Server

Networking

Storage

Virtual Machines

Access Control

Resource Monitoring

Data Protection

Scalability

Patch Management

Installing VMware ESX and ESXi

Module 2-3

Importance


Most organizations rely on computer-based services like email, 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.

Module 2-4

Module Lessons


Lesson 1: High Availability Lesson 2: Managing VMware HA Lesson 3: FT

Module 2-5

Lesson 1:High Availability


Module 2-6

Lesson Objectives


Describe VMware® solutions for: • High availability• Fault tolerance

Configure a VMware High Availability cluster

Module 2-7

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?

Module 2-8

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.

Module 2-9

VMware HA, FT, and MSCS Clustering


VMware HA FT MSCS clustering

Level of availability High availability Fault tolerance High availability

Amount of downtime Minimal Zero Minimal

Guest operating systems

supported

Works with all supported guest

operating systems

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 compatibleLimited to hardware

supported by Microsoft

UsesUse 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.

Module 2-10

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.

Module 2-11

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

Module 2-12

VMware HA in Action


vCenter Server

LUN 6LUN 5

LUN 4LUN 3LUN 2

LUN 1

host host host

virtual machine A

virtual machine B

virtual machine C

virtual machine D

virtual machine E

virtual machine F

virtual machine A virtual machine B

Module 2-13

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

Module 2-14

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.

Module 2-15

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 machinevirtual machine

virtual machine

virtual machine

virtual machine

virtual machine

Module 2-16

Architecture of a VMware HA Cluster


vCenterServer

host host host

vCenterServeragent

VMware HAagent

vCenterServeragent

vCenterServeragent

VMware HAagent

VMware HAagent

Module 2-17

Enabling VMware HA


Enable VMware HA by creating a cluster or modifying a DRS cluster.

Module 2-18

Configuring VMware HA Settings


Disable Host Monitoring when

performing maintenance

activities on the host.

Admission control helps ensure sufficient resources to provide

high availability.

Module 2-19

Admission Control Policy Choices


Policy 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 hostDedicates a host

exclusively for failover service

To accommodate organizational policies

that dictate the use of a passive failover host

Module 2-20

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.

Module 2-21

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.

Module 2-22

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

Module 2-23

Lab 23


In this lab, you will demonstrate VMware HA functionality.1. Create a cluster enabled for VMware HA.2. Test VMware HA functionality.3. Prepare for the next lab.

Module 2-24

Lesson Summary


Describe VMware solutions for: • High availability• Fault tolerance

Configure a VMware HA cluster

Module 2-25

Lesson 2:Managing VMware HA


Module 2-26

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

Module 2-27

Setting VMware HA Advanced Parameters


Set advanced parameters by

editing VMware HA cluster settings.

Module 2-28

Advanced Options to Control Slot Size


Set default (minimum) slot size: das.vmCpuMinMHz das.vmMemoryMinMB

Set maximum slot size: das.slotCpuInMHz das.slotMemInMB

Module 2-29

Planning Resources for a VMware HA/DRS Cluster


How much CPU and memory resources is the cluster using now?How much reserved capacity remains?

Module 2-30

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

Module 2-31

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

Module 2-32

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.

Module 2-33

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.

Module 2-34

Configuring Isolation Addresses


Ensure that your isolation addresses are reliable IP

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.

Module 2-35

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 inmaintenance mode.

These steps prevent unwanted attempts to fail over virtual machines.

Module 2-36

Lab 24


In this lab, you will modify slot sizes and admission control.1. Use the Resource Allocation tab to determine resource use.2. Manage VMware HA slot size.3. Configure a VMware HA cluster with strict admission control.4. Configure a VMware HA cluster with flexible admission control.

Module 2-37

Lab 25 (Optional)


Do not perform this lab unless agreed to by your instructor. In this lab, you will configure VMware HA network redundancy.1. Enable technical support mode on an ESXi host.2. Test default VMware HA failure detection time.3. Modify and test VMware HA failure detection time.4. Configure management network redundancy.5. Configure VMware HA host isolation response.6. Test network isolation functionality.

Module 2-38

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

Module 2-39

Lesson 3:FT


Module 2-40

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

Module 2-41

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.

Module 2-42

FT in Action


FT provides zero-downtime, zero-data-loss protection to virtual machines in a VMware HA cluster.

primary VM

secondaryVMnew

primaryVM

new secondary

VM

vLockstep technology vLockstep technology

Module 2-43

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

Module 2-44

How FT Works


VMkernel VMkernelVMM VMM

primaryvirtual machine

secondaryvirtual machine

record logs

read/write read

single copy of disks on shared storage

Log update? Log read?

log bufferlog buffer

Heartbeat?

Module 2-45

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

Module 2-46

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

Module 2-47

Enabling FT on a Virtual Machine


After you turn on FT, the Summary tab on the primary virtual machine

reports FT information.

virtual machine’s Summary tab

Module 2-48

Managing Virtual Machines Enabled for FT


Use the commands from the shortcut menu to test and manage the virtual machine enabled for FT.

Module 2-49

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.1. Enable FT logging.2. Activate FT.3. Test FT.4. Disable FT.

Otherwise, perform the eLearning activity:http://mylearn.vmware.com/register.cfm?course=73276

Module 2-50

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

Module 2-51

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.

High Availability

Documents

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