Tag Archives: Leave Powered On

ESXi Host Isolation Response and custom isolation address configuration.

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I was reviewing a vSphere design recently and I came across an interesting design choice which I thought I would share.

The architect selected the isolation response of “Leave Powered On” and disabled  “das.usedefaultisolationaddress”  (which is by default enabled) and configured multiple custom isolation addresses using the “das.isolationadressX” advanced setting.

The architect explained that this was done to minimize the chance of a false positive isolation event. In many environments such as ones using IP storage or where the ESXi Management VMKernel default gateway is not highly available, this can be a very good idea.

In this environment, the storage was provided via FC and the default gateway was highly available.

So was there a benefit in changing the default setting of “das.usedefaultisolationaddress” and configuring custom isolation addresses?

The short answer is No.

This is because the isolation response is configured with “Leave Powered On” so regardless of the host being isolated or not, the Virtual Machines will remain powered on.

So keep it simple, if your isolation response is “Leave Powered On” there is no need to change either of these advanced settings.

The below articles show examples of isolation response and custom isolation addresses configurations for IP Storage, FC storage and Hyper-converged environments.

Related Articles

1. Host Isolation Response for IP Storage
2. Host isolation response for FC based Storage
3. Host Isolation Response for a Nutanix Environment

Example Architectural Decision – Host Isolation Response for a Nutanix Environment

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Problem Statement

What are the most suitable HA / host isolation response when using Nutanix?

Assumptions

1. vSphere 5.0 or greater
2. Two x 10GB Network interfaces are shared for Nutanix Storage Traffic and Virtual Machine Traffic

Motivation

1. Minimize the chance of a false positive isolation response
2. Ensure in the event the storage is unavailable that virtual machines are promptly shutdown to enable HA to recover the VMs in a timely manner (where other hosts are unaffected by isolation) and to prevent a “split brain” scenario
3. Ensure maximum availability

Architectural Decision

Turn off the default isolation address and configure the below specified isolation addresses, which check connectivity to multiple Nutanix Controller VMs (CVMs) on the IP Storage VLAN.

Configure the following Isolation addresses

das.isolationaddress1 : NDFS Cluster IP Address

Configure Host Isolation Response to: Power Off

For Nutanix Controller VMs override the cluster setting and configure Host Isolation Response to “Leave Powered On”

Justification

1. The ESXi Management traffic along with the Virtual machine traffic and inter-Nutanix node storage traffic is running over 2 x 10GB connections. Using the ESXi management gateway (default isolation address) to check for isolation is not suitable as the management network can be offline without impacting the IP storage or data networks. This situation could lead to false positives isolation responses.
2. The isolation addresses chosen tests IP storage connectivity over the converged 10Gb network and in the event this is unavailable, there is no point testing further connectivity as Virtual machines cannot function without their storage
3. In the event the Nutanix cluster IP address cannot be reached by ICMP the Node will not be able to properly function. As such, triggering isolation response and powering off the VMs based on this criteria is logical as the VMs will not be able to function under these conditions.
4. In the event the NDFS Cluster IP address does not respond to ICMP on the Management interfaces it is likely there has been an isolation event OR a catastrophic failure in the environment, either to the network, or the storage controllers themselves, in which case the safest option is to Power Off the VMs.
5. In the event the isolation response is triggered and the isolation does not impact all hosts within the cluster, the VMs can be restarted by HA onto a surviving host and resume functioning
6. Using the Nutanix Controller VM (CVM) IP address (192.168.5.2) for the Isolation address is not suitable as this address exists on each ESXi hosts and as such it is not a good candidate for isolation detection as the host will always be able to find this address even when the network is offline due to the CVM being local to the host
7. The Nutanix Controller VM accesses local storage and can continue to run locally even in an isolation event. When the isolated event is over, the CVM will then regain connectivity to the other CVMs in the Nutanix cluster.
8. Shutting down the CVM would only increase the recovery time once the isolation even is over and has no added benefits.

Implications

1. In the event the host cannot reach any of the isolation addresses, virtual machines will be powered off.
2. Initial cluster setup would require the vSphere administrator to override the Cluster settings for each Controller VM. Note: This is a one time task (Set & Forget)

Alternatives

1. Set Host isolation response to “Leave Powered On”
2. Do not use Datastore heartbeating
3. Use the default isolation address
4. Leave the CVM on the default cluster setting and “Shutdown” on isolation

Related Articles

1. VMware Host Isolation Response in a Nutanix Environment #NoSAN

2. Storage DRS and Nutanix – To use, or not to use, that is the question?

3. VMware HA and IP Storage

VMware Host Isolation Response in a Nutanix Environment #NoSAN

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I was recently discussing the Nutanix solution with a friend of mine and fellow VCDX, Michael Webster (@vcdxnz001) and he asked what the recommended Host Isolation Response is for Nutanix.

At this stage I must advise there is no formal recommendation, but an Official vSphere on Nutanix Best Practice guide is in the works and will be released asap.

Back to my conversation with Michael, Being that Nutanix is an IP Storage solution, my initial feeling is that Host isolation Response should be set to “Shutdown”, but I didn’t go into any more detail with Michael, so I thought it best to post a quick explanation.

This post also assumes basic knowledge of vSphere as well as the Nutanix platform, for those of you who are not familiar with Nutanix please review the following links prior to reading the remainder of this post.

About Nutanix | How Nutanix Works | 8 Strategies for a Modern Datacenter

So back on topic, in other posts I have written for IP Storage, such as (Example Architectural Decision – Host Isolation Response for IP Storage) I have concluded that “Shutdown” was the most suitable setting and recommended specifying isolation addresses of the NAS controllers.

But as Nutanix changes the game and has one virtual storage controller per ESXi host, so does this change the recommendation?

In short, No, but for those who are interested, here is why.

If we leave the default isolation address, (being the default gateway for ESXi Management), in the event the gateway is down, it will trigger an isolation response even if the rest of the network is operating fine, thus an unnecessary outage would occur.

If we configure das.isolationaddress1 & 2 with the Management IP address of any two Nutanix Controller VMs (192.168.1.x , 192.168.1.y in my below diagram) then an isolation response will only be triggered if both Nutanix Controller VMs (CVMs) are not responding, in which case, the VMs should be Shutdown as the Nutanix cluster may not be function properly with two Controllers offline concurrently as its configured by default for N+1 (or replication factor of “2” in Nutanix speak).

The below is a high level example of the above configuration.

NutanixHostIsolation

Related Articles

1. Example Architectural Decision – Host Isolation Response for a Nutanix Environment

2. Storage DRS and Nutanix – To use, or not to use, that is the question?

3. VMware HA and IP Storage