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Setting a concurrent power operations rate to support View desktop logon storms (2015557)

Details

During a View desktop logon storm, in which some desktops started in a powered off state, some logons might fail. View Clients display the following error message: "The assigned desktop source for this desktop is not currently available. Please try again later."

The following message appears in the View Connection Server DEBUG logs: "Limits exceeded for operation on <VMname> lockId: <Managed object ID>, queuing for later"
 
Typically, this message means that a concurrency limit was reached. In this case, the vCenter Server concurrent power operations limit was reached.


Solution

If a desktop is powered off when a user attempts to connect to it, View powers it on to satisfy the connection request. The maximum number of concurrent power operations is governed by the Max concurrent power operations setting for a vCenter Server instance. Starting in View 5.0, this limit is set to 50 by default.

The required number of concurrent power operations is based on the peak rate at which desktops are powered on and the amount of time it takes for the desktop to power on, boot, and become available for connection. In general, the recommended power operations limit is the total time it takes for the desktop to start multiplied by the peak power-on rate.

For example, the average desktop takes two to three minutes to start. Therefore, the concurrent power operations limit should be 3 times the peak power-on rate. The default setting of 50 is expected to support a peak power-on rate of 16 desktops per minute.

View waits a maximum of five minutes for a desktop to start. If the start time takes longer, other errors are likely to occur. To be conservative, you can set a concurrent power operations limit of 5 times the peak power-on rate. With a conservative approach, the default setting of 50 supports a peak power-on rate of 10 desktops per minute.

Logons, and therefore desktop power on operations, typically occur in a normally distributed manner over a certain time window. You can approximate the peak power-on rate by assuming that it occurs in the middle of the time window, during which about 40% of the power-on operations occur in 1/6th of the time window. For example, if users log on between 8:00 AM and 9:00 AM, the time window is one hour, and 40% of the logons occur in the 10 minutes between 8:25 AM and 8:35 AM. If there are 2,000 users, 20% of whom have their desktops powered off, then 40% of the 400 desktop power-on operations occur in those 10 minutes. The peak power-on rate is 16 desktops per minute.

Tags

View, power operations, I/O storms

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