The purpose of this contribution
Sometimes there is a small change adds great value or mitigates a pain point. This post today is about one of those small changes. With XenDesktop 7.6 a new setting "Simultaneous Personal vDisk inventory updates (absolute)" was added to the hypervisor connection screen called. But to appreciate the present, it is important, the past and the pitfalls presented it to understand. So we go back to XenDesktop 7.5, touch base on some required background and understand the problem first.
The essence of
Image Update [1945004[
Since this post is primarily about PvD, it is important what image understand -Update means in connection with the PvD.
Briefly, image update or catalog update is the process, all of the desktops in a modernizing equipment catalog to a single updated master image. This is also called the state "preparation" in the studio. It consists of two steps
- updating the master image
- to the XenDesktop catalog Upgrade
For PvD this also means re-calculate the affected data on PvD for it be to work in a position with the new base image. Moreover, this process also the equipment update includes undergo restart. carry details on-screen update steps and follow this link
hypervisor throttling. What and Why
In XenDesktop, hypervisor throttling the number of concurrent actions of a certain type of configuration settings are limited by a mechanism. This includes actions such as power actions and PvD prepare state
1 is the " Edit connection "window of XenDesktop 7.5. here under "To edit a connection" Details about how to reach the window section. The configuration fields in the picture show how XenDesktop controls key parameters such as concurrent actions on a hypervisor. These limits are necessary because the hardware infrastructure can handle only a limited number of such actions at a time.
Before we can get to the core of this point, it is important to the settings that presents this window to understand. Below is a brief description of each of them .:
It is important that these settings for the collection of all machines for a particular hypervisor connection
- Maximum apply note active measures : This is the maximum number of performance actions that can be performed at any time
- maximum new actions per minute . This number of new actions that may be, every minute started
- Maximum power actions. As a percentage of desktops the percentage of total VMs for the hypervisor connection configured that can go through the competing actions. The effect is substantially the same as' maximum active measures ", so the value is expressed as a percentage and not the absolute number
- Maximum Personal vDisk power actions as a percentage . A bit of a false name, this setting actually controls the number of PvD machines, which may be the same in the preparation state at any point of time. As the name suggests, however, that there actions applies to the PvD machines to power.
also note that whenever the same setting of two fields is controlled, is called the absolute number, and the other refers to the percentage of the value of the number of machines corrects lower, is the one that takes effect .
is our focus be put on point 4 above. "maximum Personal vDisk power actions as a percentage". The preparatory state for a PvD machine (also known as image-update) is a memory-intensive operation IOPS and is on the storage / hardware infrastructure dependent.
Back to the main point ...
By now we have learned three important things .:
- , the settings on the screen on the hypervisor connection to all machines
- screen update is an intensive operation that is directly related to the storage and hardware infrastructure.
- , the number of machines PvD image update is controlled at any time by a number of passes, which is a percentage of the total number of machines on the hypervisor connection.
The thing about percentages - them to solve larger numbers, as the whole is growing. The "whole" is controlled by the hypervisor connection here the number of machines.
So what all essentially boils down from this is the fact that the "Maximum Personal vDisk power actions as a percentage", which we discussed earlier, the number of machines for a certain percentage figure means that, if the number of machines to increase under the hypervisor connection, the state for the same hardware at the same time be higher now in preparation.
This means that the same hardware must now support more simultaneous image update operations compared to before. There is an obvious problem here. The number of machines image update at a point of time have run increases where as hardware support underlying is unchanged.
How do we solve this problem? One way to do this is to have an absolute number, and not the percentage. While we already have a percentage and an absolute number for "Maximum Power Actions", the absolute number of missing PvD preparatory state.
Enter XenDesktop 7.6 ...
Regarding the issue that we discussed above, we put things with XenDesktop 7.6 to improve from.
2 is a screenshot of the same settings screen in the new XenDesktop version.
as can be seen, the screen is informative, explains how the absolute and percentage values in connection work together. Also we have an absolute value setting for "Simultaneous Personal vDisk inventory updates", together with the percentage value and the setting name makes more sense. The value that dissolves the reduced number of machines to take effect.
So now the administrator has the option for the hardware infrastructure to provide an absolute number of PvD machines and would not change this value when a new machine coming under the hypervisor connection. The administrator can set the percentage value to a high value when the number of concurrent machines in preparation state wants to be affected by the total number of machines under the hypervisor connection. This would cause the absolute value to occur, because that is the lower value.
Alternatively if the administrator is satisfied with the settings, it had set in XenDesktop 7.5 (assuming that it has been updated to XenDesktop 7.6) they can use the percentage and provide the absolute value to a much higher number on, so that the percentage is effective.
I hope that helps administrators understand the intricacies of this setting. Keep an eye out for a future post about how to choose the optimal value for this setting.
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