Home > Storage > PowerStore > Virtualization and Cloud > VMware Horizon 8 with Dell EMC PowerEdge R6525 Servers and Dell EMC PowerStore 9000 > Log off and refresh
When a user logs off an instant clone VM, it is refreshed to match the current gold image. In this test, Login VSI logs off all 2,500 users at the end of steady state in about 13 minutes. Log off is followed by a period of increased I/O, bandwidth, and CPU demand on the PowerStore appliance as the VMs refresh. In this test, the mass log off and refresh of 2,500 desktop VMs completes in about two hours.
In most user environments, user log in and log off occur gradually at the beginning and end of the workday. VMs refresh gradually instead of all at once as in this test. There may not be clear distinctions between the different phases in a work environment where log in and log off events happen gradually. This test is configured so that all logins and log offs occur within narrow time windows to stress the environment.
Horizon settings can be adjusted to increase refresh rates if desired, but this increases storage I/O and CPU demand. If a PowerStore appliance is hosting other workloads in addition to VDI, a period of sustained activity after a mass log off must be accounted for in the overall performance of the appliance.
During refresh, storage IOPS, bandwidth, and CPU demand increase with brief spikes in latency.
The storage experiences a sustained period of increased I/O, bandwidth, and CPU demand during the log off and refresh phase. However, host server CPU usage diminishes during this phase.
The server iDRAC9 also shows a similar drop in CPU usage during refresh on each PowerEdge host.