I am posting the Q&A for the TechTalk we had on XenApp Power and Capacity Management. It was well attended (more than 50 customers and partners) with lots of time for Q&A. Check out the webinar recording if you were not able to attend.

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Q) How does a combination of XenServer with virtual XenApp work? So, is it possible to first shut down the unnecessary XenApp servers and then the unnecessary physical servers running XenServer?

A: Power and Capacity Management does not manage the XenServers themselves. It only manages XenApp servers. So, if you have no virtual XenApp servers running on a XenServer it will still be powered on. Why? You may still have non-XenApp workloads running there like web servers or e-mail servers, etc. But you can use other management tools to power manage the hypervisor.

Q) Will it be possible to install the PCM agent in a "standard" provisioning server image?
A: Yes. Power and Capacity management works with Wake on LAN which is how provisioning server works to deliver images to bare metal. Wake on LAN is supported in addition to virtual machines for Power and Capacity Management.

Q) So, Can I provision my XenApp servers with provisioning server and the collector gets the different names of the server or is a special configuration needed?
A: Yes. When you install the agent, there is a configuration for Wake on LAN or Virtual machines. You select Wake on LAN and configure accordingly for the image you are creating.

Q) Must I also choose "Wake on LAN" if the provisioned XenApp server is a virtual server on XenServer?
A: You can have a single PVS image to work across physical or virtual deployments. Even when using PVS, if you are booting servers via XenServer, you would choose XenServer. If you are booting via Wake on LAN on the physical hardware then you would choose Wake on LAN

Q) Can PCM and SCOM work together?
A: Out of the box, we are not planning any integration with operations manager. However, everything being done through the GUI can be done through WMI, so this can be customized.

Q) Should the concentrator be installed on a XenApp server?
A: No. You do not want to install this on a XenApp server that hosts users sessions. You won't be able to power manage it if you do. Also, concentrators can manage servers across farms so you want a farm-independent server if you can do so.

Q) Instead of number of sessions, is there a way to set the Capacity by percentage of Server resource utilization e.g. CPU, RAM, Page File Usage?
A: Yes. We are enabling you to use nominal capacity (sessions) or load evaluator and have this all calculated as a percentage of load evaluator. This will be enabled in the final release but is not available in the technology preview.

Q) In terms of new session distribution, what takes precedence, the XenApp load evaluator or the Power and Capacity Management evaluator?
A: Power and Capacity Management takes precedence for server power on/off and consolidation only. For load distribution, the XenApp load evaluators are used.

Note that PCM adjusts the load evaluation for servers that are not selected to receive sessions. PCM will keep up to "Minimum Available Servers" available for logon. Other servers' load evaluators will be set to 20,000 (you will see that if you run QFARM /load).

Q) I am wondering how server monitoring will have to be modified to allow for servers "shutting down" and suppressing alerts. Do you have any examples of solutions?
A: EdgeSight already differentiates between planned and unplanned reboots. Since reboots initiated by PCM will be planned reboots, you should be able to create alerts only for unplanned reboots

Q) Can you please explain the process of draining a server. We publish the desktop so we have some users logged on for 8+ hours. Also we have shift workers.
A: PCM selects up to "Minimum Available Servers" to accept logons. All other servers have their LE values set to 20,000 and therefore won't be selected to host apps/desktops. When an available server reaches the optimal load, the server with highest load, but under optimal load, is chosen to receive logons.

Draining is a  side-effect of the model above. As shift workers start to login, they will do so on the highest loaded servers under optimal load policy. As the previous shift logoff, their servers will automatically drain until empty. The new shift will only consume enough servers to meet its demand.

Q) If you provision server through PVS with the agent already installed and configured for a workload called "office 2003", if you want to change the workload to "office 2007" would you need to change or create a new PVS image to reflect this change?
A: Workloads can be assigned via GPO, so it's possible to use the same PVS image for more than one PCM workload. In the example above, if Office was virtualized via App-V or Streaming, then the same image could be used.

During the Tech Preview of Workflow Studio, the most popular posts I had were around using Workflow Studio to create a green data center:

• Green Data Center - Support for Wake On LANhttp://community.citrix.com/x/RQUgAg

• Green Data Center - Getting the power back on
  http://community.citrix.com/x/AQUgAg

• Green Data Center - Shutting Down a Windows Server
  http://community.citrix.com/x/9IUNAg

• Green Data Center - Shutting Down a XenServer Host
  http://community.citrix.com/x/1IAVAg

I wanted to review these very popular posts and talk about how the most recent versions of Workflow Studio can be leveraged for these tasks.

Wake On LAN
Support for WakeOnLAN was included in the activity library pack made available in April with version 1.1. The WakeOnLAN activity is in the 'Networking' library and in the 'Networking' folder in the Designer once installed:

Shutting Down a Windows Server
In the Tech Preview post, I talked about two methods of shutting down a computer. One of those two methods - LaunchProcess - is available as part of the library pack that was released in April (under Windows), but also in that pack is a Shutdown activity that manages this for you. The Shutdown Windows activity is in the Networking library with Wake On LAN.

Shutting Down a XenServer host
In the Tech Preview post, I talked about several activities for interfacing with XenServer VMs and the XenServer host. These activities are all part of the library pack from April. These activities are in the 'Citrix XenServer' library and in the 'Citrix XenServer' folder in the Designer once installed:

The host activities Disable-Host and Shutdown-Host that were in the Tech Preview post are not available yet, but will be in the next update to this library.

If you are using Workflow Studio to manage power in your environment, drop me a line and let me know how it is going. If you aren't using it, let me know what we can do to make it easier for you.

In a previous post I covered how to integrate Wake On LAN into your workflow, but how many people are currently using Wake On LAN or at least know that the majority of their servers support it?

Do the servers in your Data Center support Wake On LAN technology?	Choose
Yes, and I currently use it
Yes, I believe so but I am not using it
No, they only support the hardware vendor's proprietary technology
No, they do not support any form of remote power management
I have no Idea

In previous posts I have explored using Workflow Studio to Shut down a Windows host and also how to Shut down a XenServer host. Getting the power off is a big step in being greener, but if you could just turn off machines and leave them off permanently then you wouldn't need Workflow Studio Next we have to look at how to get those hosts powered back on.

There are a lot of different options out there for power management, but the one thing that is fairly consistently avaiable is Wake On LAN (WOL). In this post I am going to look at how WOL technology can be leveraged by Workflow Studio. Most modern server NICs have some form of WOL support (though you may have to turn it on in the BIOS.) This allows you to start up any machine that you know the MAC address for. Heare are some details on WOL from Intel and the Wikipedia WOL page has a good overview and a lot of links to free utilities and sample code.

Now that we have an understanding of how we want to start our server we can add it in as a task in Workflow Studio. There isn't a native WOL task in Workflow Studio (not yet anyway), but it is pretty easy to call one of the tools mentioned in the Wikipedia article with a "Launch Process" task. I started with that, but didn't like having to require one of these to be installed, so I went looking at the code samples. I finally found a great implementation of WOL in PowerShell by /\/\o\/\/ The PowerShell Guy. Paste that code in a PowerShell Script task and you have an embedded Wake On LAN task.

The next step is to put all this together into a single workflow with some business logic about when you want to start and stop your servers. I want to hear from you - what metrics would you want to use to drive a "Green" workflow? Is Wake On LAN supported in your data center? What issues do you have that this kind of a workflow could help with?

Shawn Bass wrote a good blog about the new PowerSmart Utility

In his blog, he explained his take on our choice of of using WinRm and server vendors's out of band management products. It's a good read.

One thing I need to clarify is that it is fairly simple to configure this version of PowerSmart to power on HP servers if you follow the user guide. We'd like to hear your experience and improve the tool and its documentation.

Shawn was right that if you just want to give the tool a quick try without reading much, the out of the box default configuration will allow you to try it without much restriction. It will even work in a virtualized environment.  Please see the minimum requirement section of the download page. The trade-off however is that this default configuration won't power on servers. A good default power on mechanism is hard to find because user environments are likely to be very different.  The included HP script won't work with IBM servers for example. We thought this default is a safer option and it can lead the users to think about the best way to power on servers. Plus this default makes it easier for users to have an alternative mechanism to power on servers. For example, users can use windows scheduler to schedule a script to power on servers. Yes, the HP scripts we provided can be easily modified to do so.

We thought about using Wake On LAN as default. But we soon realized that it has many limitations too. Please see the FAQ page for more details. However If you know WOL well or you can get some experts such as Shawn to help, it may very well work for you.  I heard a large company had successfully used WOL to save millions of dollars by powering off idle desktops. In the data center, I expect administrators may have more control over the servers and thus WOL may have a higher chance to be useful.

Please share your experience with others so that we can benefit from each other.