Tag Archives: Power Off

Example Architectural Decision – Horizon View Desktop Power Policy for Linked Clones (1 of 2)

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Problem Statement

In a VMware Horizon View environment using persistent Linked Clones, Disposable disks are being used to redirect transient paging and  temporary files to a separate VMDK.

What is the most suitable Desktop Pool setting to ensure storage overheads are reduced?

Assumptions

1. VMware View 4.5 or later
2. Recompose / Refresh cycles are infrequent
3. Desktop Usage concurrency within the pool is less than 100%
4. Memory Reservations are not being used.

Requirements

1. The environment must deliver consistent performance
2. Minimize the cost/utilization of shared storage

Motivation

1. Reduce complexity where possible.
2. Maximize the efficiency of the infrastructure

Architectural Decision

Set the Power Policy for all Linked Clone desktop pools to “Power Off”

Justification

1. Using disposable disks can save storage space by slowing the growth of linked clones and reducing the space used by powered off virtual machines.
2. Using the “Power Off” policy for the pool means at user logoff (or shutdown) the disposable disk will be refreshed, therefore reducing the capacity usage at the storage layer.
3. “Powered Off” VMs do not have a Virtual Machine SWAP file which will also reduce storage consumption.

Implications

1. Setting the policy to “Power Off” will result in more frequent power operations which may impact the performance of the storage and vCenter.
2. When a user attempts to login to a desktop which has been powered off, there will be a delay while the VM is powered on and booting up before the user will be logged in.
3. The peak concurrency rate of users will need to be understood to allow accurate storage planning for the VSWAP file.

Alternatives

1. Increase the frequency of Recompose / Refresh / Rebalance operations
2. Set the Policy to “Take no power action” and schedule an Administrator task to periodically change the Power Policy to “Powered Off” during a maintenance window.
3. Set the Policy to “Ensure desktops are always powered on” and schedule an Administrator task to periodically change the Power Policy to “Powered Off” during a maintenance window.
4. Set the Policy to “Suspend”  and schedule an Administrator task to periodically change the Power Policy to “Powered Off” during a maintenance window, however this will consume extra storage for the Suspend File.
5. Use Memory Reservations to reduce storage requirements for vSwap and leave Power Policy to “Always On”.

Related Articles:

The example architectural decision was contributed to by Travis Wood (@vTravWood) and was inspired by the following article:

1. Understanding View Disposable Disks by @vTravWood (Double VCDX #97 Desktop/Datacenter Virtualization)

1. Transparent Page Sharing (TPS) Configuration for VDI (1 of 2)

2. Transparent Page Sharing (TPS) Configuration for VDI (2 of 2)

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