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VDI test configuration
13 Dell EMC SC Series: 3,000 VMware Horizon Linked Clone VDI Users | 4735-RA-V
3.2 Improving VM performance
3.2.1 Memory
Virtual machine performance is greatly affected by the quantity of memory allocated to each VM. It is the most
effective way to improve performance in virtual machines, but it can be difficult to scale to large environments
because of the aggregated quantity. For the purposes of this scenario, 3 GB per VM is allocated.
Decreasing allocated memory results in more storage load, and this impact on storage should be tested.
Creating a baseline for a single VM gives a good indication of storage load per VM. This provides a starting
point for I/O load, but many other factors affect the total.
3.2.2 Host-based caching
The host configuration can change the load generated to the storage. One of the options is content-based
read cache, enabled through Horizon View Storage Acceleration. This option uses host RAM to accelerate
reads during boot events. This can reduce volume reads and improve boot times for virtual machines. The
tradeoff is increased host memory load. On hosts that are memory-constrained, this may not be an option.
For those that can spare memory, this can improve the boot times of the virtual machines when large
numbers of machines are requesting the same data.
3.2.3 VMware OS optimization
VMware offers a free tool to optimize virtual machines. It is a profile-based optimization tool that can greatly
reduce the resource requirements for virtual machines.
Login VSI has created a profile for VM optimization that reduces memory, disk, and CPU requirements to
allow a greater number of virtual machines per host. It can have a negative impact on some applications so
testing is required. The overall impact to is considerably reduce host requirements for virtual machines
allowing a much greater number per host.
The Windows
®
10 Login VSI profile was used to optimize tested machines. Find more information in the Login
VSI article Optimizing desktop images with VMware OSOT. Login VSI provides guidance on how the profile
changes the behavior of virtual machines when applied.
Testing should be done once an optimization profile has been applied to ensure users are still able to use the
desktops. The modifications favor performance and may require tuning to allow all applications to function
correctly.
Testing for VDI load requires many interconnected systems and processes. A test harness needs to connect
to all of the VMs and generate a realistic load. The load needs to perform at a level deemed acceptable to
users.