In a Horizon 7 environment, logon storms are the main consideration when determining bandwidth requirements.
Although many elements are important to designing a storage system that supports a Horizon 7 environment, from a server configuration perspective, planning for proper storage bandwidth is essential. You must also consider the effects of port consolidation hardware.
Horizon 7 environments can occasionally experience I/O storm loads, during which all virtual machines undertake an activity at the same time. I/O storms can be triggered by guest-based agents such as antivirus software or software-update agents. I/O storms can also be triggered by human behavior, such as when all employees log in at nearly the same time in the morning. VMware has tested a logon storm scenario for 10,000 desktops. For more information, see View Composer Performance Test Results.
You can minimize these storm workloads through operational best practices, such as staggering updates to different virtual machines. You can also test various log-off policies during a pilot phase to determine whether suspending or powering off virtual machines when users log off causes an I/O storm. By storing View Composer replicas on separate, high-performance datastores, you can speed up intensive, concurrent read operations to contend with I/O storm loads. For example, you can use one of the following storage strategies:
Manually configure the pool settings so that replicas are stored on separate, high-performance datastores.
Use Virtual SAN, available with vSphere 5.5 Update 1 or later, which uses Software Policy-Based Management to determine which kinds of disks to use for replicas.
Use Virtual Volumes, available with vSphere 6.0 or later, which uses Software Policy-Based Management to determine which kinds of disks to use for replicas.
In addition to determining best practices, VMware recommends that you provide bandwidth of 1Gbps per 100 virtual machines, even though average bandwidth might be 10 times less than that. Such conservative planning guarantees sufficient storage connectivity for peak loads.