Solved

High Availability and failover

Posted on 2014-02-21
8
309 Views
Last Modified: 2014-03-10
i would like to know what is the time interval allowed between heartbeats initiated by ESX host before the failover kicks in.

In other words, if ESX hosts has not heard from on of the other ESX hosts in the cluster, for a certain period of time, then they can declare it down, and start rebooting the VMs residing on the Defunct Host , from other hosts

I also want to know if there is a network outage where one ESX host is located on, or 2 of the ESX hosts are located on, would this initiate reboot of VMs on the other hosts.
I know this is very rare, because there is switch redundancy, but it can happen..

Thanks
0
Comment
Question by:jskfan
  • 4
  • 4
8 Comments
 
LVL 119

Assisted Solution

by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 500 total points
ID: 39879039
i would like to know what is the time interval allowed between heartbeats initiated by ESX host before the failover kicks in.

In other words, if ESX hosts has not heard from on of the other ESX hosts in the cluster, for a certain period of time, then they can declare it down, and start rebooting the VMs residing on the Defunct Host , from other hosts

The Time Interval is 10 seconds, these values can be changed, but the defaults are recommeded by VMware.

I also want to know if there is a network outage where one ESX host is located on, or 2 of the ESX hosts are located on, would this initiate reboot of VMs on the other hosts.
I know this is very rare, because there is switch redundancy, but it can happen..

Yes, this can happen, because VMware HA, and the ESXi servers, are checking each other, and checking they can reach the default gateway.
0
 

Author Comment

by:jskfan
ID: 39880091
10 seconds , that sounds too short… this can cause reboot of VMs, that's what I believe……..
0
 
LVL 119

Assisted Solution

by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 500 total points
ID: 39880337
If you networking is that poor.

Is your networking and physical switches likely to be unavailale for 10 seconds?
0
Netscaler Common Configuration How To guides

If you use NetScaler you will want to see these guides. The NetScaler How To Guides show administrators how to get NetScaler up and configured by providing instructions for common scenarios and some not so common ones.

 

Author Comment

by:jskfan
ID: 39880583
I got the following paragraph from Vmware:

=========
Network Isolation Addresses
A network isolation address is an IP address that is pinged to determine whether a host is isolated from the network. This address is pinged only when a host has stopped receiving heartbeats from all other hosts in the cluster. If a host can ping its network isolation address, the host is not network isolated, and the other hosts in the cluster have failed. However, if the host cannot ping its isolation address, it is likely that the host has become isolated from the network and no failover action is taken.
By default, the network isolation address is the default gateway for the host. Only one default gateway is specified, regardless of how many management networks have been defined. You should use the das.isolationaddress[...] advanced attribute to add isolation addresses for additional networks. See vSphere HA Advanced Attributes.
=================

what I do not understand is, when the host can OR cannot ping its default gateway , what would happen?
 I know most of environment do not dedicate a networked isolation address, since the default gateway address can be used..
0
 
LVL 119

Assisted Solution

by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 500 total points
ID: 39880599
If the gateway is not reachable, a worker process is started to determin to start HA failover...

VMware HA starts the process of deciding whether to start the VMware HA process.

e.g. a workflow procedure is started, eg. it starts writing to datastores, it checks if all Hosts in the Cluster are contactable, it does not just say, oh, cannot ping the gateway, therefore, I must now failover!!!!

different isolation addresses are used, normally the default gateway is used, because it shoudl always be available in your network.
0
 

Author Comment

by:jskfan
ID: 39880839
<<However, if the host cannot ping its isolation address, it is likely that the host has become isolated from the network and no failover action is taken.>>>
if you read the above excerpt from vmware, the way they stated it , is no failover action is taken when the host cannot ping the isolation address.
however the way I understand is the failover  will indeed take action when the host cannot ping the isolation address (assuming we are using DG only)
0
 
LVL 119

Accepted Solution

by:
Andrew Hancock (VMware vExpert / EE MVE^2) earned 500 total points
ID: 39880912
Many intervals and timings are used to determine if and when to initiate a VMware HA failover.

(and you've got Host Failure and VM failure and restart)

The HA agents on the servers, also check they can reach Master and Slave HA Agents (FDM Agents).
0
 

Author Closing Comment

by:jskfan
ID: 39918120
Thank you
0

Featured Post

U.S. Department of Agriculture and Acronis Access

With the new era of mobile computing, smartphones and tablets, wireless communications and cloud services, the USDA sought to take advantage of a mobilized workforce and the blurring lines between personal and corporate computing resources.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
San to San Replication Slowness/Issues 3PAR 7000 5 43
VCenter migration issue 10 71
Combining 2x Windows VCenter to 1x VCSA ? 9 45
VMware - ESXi Cost and features? 2 42
Exchange server is not supported in any cloud-hosted platform (other than Azure with Azure Premium Storage).
In this step by step tutorial with screenshots, we will show you HOW TO: Enable SSH Remote Access on a VMware vSphere Hypervisor 6.5 (ESXi 6.5). This is important if you need to enable SSH remote access for additional troubleshooting of the ESXi hos…
Teach the user how to install and configure the vCenter Orchestrator virtual appliance Open vSphere Web Client: Deploy vCenter Orchestrator virtual appliance OVA file: Verify vCenter Orchestrator virtual appliance boots successfully: Connect to the …
Advanced tutorial on how to run the esxtop command to capture a batch file in csv format in order to export the file and use it for performance analysis. He demonstrates how to download the file using a vSphere web client (or vSphere client) and exp…

837 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question