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)