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VDI environments are typically heavily biased towards writes. This bias occurs because once the VMs are booted, the I/O traffic includes mostly changes from each VM. The traffic consists of file changes, swap file writes, memory paging, and updates to user preferences. This traffic pattern makes VDI one of the more demanding applications.
The heavy write ratio of VDI requires more attention to be focused on the number of writes that are generated and the rate of change to the environment. For environments that are persistent, these factors should be accounted for when snapshots are taken. The average snapshot size is larger because of the rate of change occurring.
If persistence is maintained at the VM level and profile redirection technology is not used, the VM volumes must be larger. The snapshot growth is larger as well.
Instant clones generate a large volume of traffic during the provisioning process due to the method used to create the VMs. Since the in-memory VMFork technology creates the machines quickly, the volume of traffic is significant. The I/O required to complete the creation is brief but large. Plan for bursts of high traffic when creating or refreshing instant clone machines. These bursts of high traffic may impact other workloads if a PowerStore appliance is not dedicated to VDI. For a large VDI implementation, a PowerStore appliance should be dedicated to VDI.
Instant-clone machines reset on logout. As users log off, their virtual desktops refresh automatically. This action occurs throughout the workday and should be considered in the design. Virtual desktop refreshes cause a brief spike in IO that is proportional to the number of desktops refreshing at any given time. If many desktops refresh simultaneously, the I/O demand will spike as they refresh.