White Papers

Sizing and Best Practices for Deploying VMware View 4.5

on VMware vSphere 4.1 with Dell EqualLogic Storage

3.4.1 Using Linked Clones

You can realize significant storage space savings and increased efficiencies in client VM provisioning

and administration when using linked clones. To setup a linked clone pool, you first create a “parent”

VM image with the required OS, settings and software installed. View Composer will coordinate with

vCenter to create a pool of linked clones, using the parent VM image as the base image for the clones.

Each linked clone functions as an independent desktop VM with its own unique identity. Linked clones

share the base image as their OS image and thus consume significantly less storage space than a

complete independent VM image. Temporary system data as well as user data unique to each linked

clone desktop VM is written to storage separately. This temporary data can be deleted at the end of

the session. Persistent data such as user profile and application/user data can optionally be redirected

to a persistent storage location assigned to each desktop VM. Thus software maintenance updates and

patches need only be applied only to the base image to take effect on all linked clones, without

affecting any unique user settings and data.

View composer first creates a full replica of the parent VM, and then uses that replica to create linked

clones. The replica can be placed on the same datastore as the linked clones, or on a separate

datastore. By placing the replica on a separate datastore, you have the opportunity to use high

performance storage (SSD) for storing the parent image for the linked clones. This strategy can lead to

significant I/O performance gains in View VDI infrastructures.

4 VMware View 4.5 Characterization Tests

The objective of our testing was to measure VMware View VDI I/O workloads and determine scale-out

guidelines for how many virtual desktop clients can be supported by Dell EqualLogic SANs. From the

storage perspective, the primary limits governing how much you can scale a virtual desktop

infrastructure are the storage capacity and the maximum sustained IOPS that your storage system can

provide, while staying below acceptable I/O latency limits. The VDI storage system needs to be able to

sustain the required IOPS per desktop while staying within acceptable read/write I/O latency limits.

The typical industry standard latency limit for I/O reads and writes is less than 20ms. This limit will

result in good user application response times (assuming no other infrastructure components become

a bottleneck). For capacity, we provisioned a minimum of 2GB storage on average per linked clone

delta disk.

We used VMware’s VDI load generation tool named Reference Architecture Workload Code Simulator

(RAWC) to simulate full scale VDI workloads while measuring system I/O performance. RAWC consists

of a controller server and scripts installed on each VDI client. The tool launched View Client Sessions

(via session launcher VMs) into the desktop VMs hosted in the View infrastructure. Within a desktop

Note: See the “Creating Desktop Pools” section in the

VMware View Online Library

for more information about how to configure Linked Clones:

 http://pubs.vmware.com/view45/ol/