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Causal note:

Phew, I just had good weekends with friends playing paintball. All my muscle are aching and sore this morning. I recommend everyone to try it at least once in your life. Please remember to wear protections because I just shoot a guy right in the crotch.  ho ho…

Right. Let’s back to business. As you guys may know, I’m preparing VCAP-DCA as well. There are some nice blogs on the Internet. I am trying to add some of my own understanding. Enjoy.

Section 4 – Manage Business Continuity and Protect Data

Objective 4.1 – Implement and Maintain Complex VMware HA Solutions


Identify the three admission control policies for HA

According to Yellow brick, it has Host failures cluster tolerates(Slot calculation), Percentage of cluster resource, specify a failover Host.

Identify heartbeat options and dependencies

Heartbeat is ping message from Secondary Host to Primary Host and between Primary hosts. The default failover heartbeat threshold is 15 secs.

Das.failuredectiontime settings change time limit.

Das.isolationaddress gives you additional host to ping.

Skills and Abilities

Calculate host failure requirements

Host is not able ping other primary host. Host is not able to ping gateway or other special server dedicated by das.isolationaddress.

Configure customized isolation response settings

failover heartbeat threshold is 15 secs.

Das.failuredectiontime settings change time limit.

Configure HA redundancy in a mixed ESX/ESXi environment

I don’t see any particular requirement for ESXi except if you only want to use one nic for everything. You may need to setup das.allowNetwork

Configure HA related alarms and monitor an HA cluster

Create a custom slot size configuration

Slot is maximum reservation of CPU and memory on a given host. If there aren’t any reservation of small reservation, it use 256MHZ for CPU and 0 memory for slot.

You can customize slot size by editing das.slotCpuInMHz and das.slotMemInMB.

If you have 25 CPU slots but 5 memory slot, the available number of slot for this host is 5.

In version 4.1, HA will ask DRS to make change.

If  you customize the slot, you need to be careful for special big reservation vm which may or may not work. DRS may or may not help.

Understand interactions between DRS and HA

IN the version 4.1, the HA may request DRS to move VM around in terms of freeing some resource. But a guarantee can’t be given.

Create an HA solution that ensures primary node distribution across sites

The key for HA crossing is more suitable for blade system. Need to make sure each chasse has it’s own primary HA Host.

You can use

Cat /var/log/vmware/aam/aam_config_util_listnodes.log

To find out which hosts are primary.

Another method of showing the primary node is  /opt/vmware/aam/bin/cli

Reelection occur at

  • Switch to maintenance mode
  • Disconnect from cluster
  • Remove from Cluster
  • Reconfig for HA

Analyze vSphere environment to determine appropriate HA admission control policy

If you have a dedicate Host (which has different CPU and memory), it’s more likely you would use Designated failover host.

If you don’t mind to manually calculate percentage of resource. Don’t setup unbalanced clusters percentage too low, percentage reserved can be a good option.

Amount of host failures is a transitional way. It can be inflexible and conservative.

Analyze performance metrics to calculate host failure requirements

This is a long story and best way is to check out Yellow brick, HA Deepdive.

I’m trying to summarize whatever I understand. Please tell me if I miss anything.

Analyze Virtual Machine workload to determine optimum slot size

Analyze HA cluster capacity to determine optimum cluster size

Tools

vSphere Availability Guide

• Product Documentation

• vSphere Client

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One Comment

  1. Configure HA redundancy in a mixed ESX/ESXi environment
    I don’t see any particular requirement for ESXi except if you only want to use one nic for everything. You may need to setup das.allowNetwork

    perhaps this is really das.allowVmotionNetworks


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