To all the people out there who had issues when trying to create a machine catalog on versions above 7.9 and wondered why the Disk Cache option is greyed out, here is a potential answer to that issue. This is exactly what I ran into while recreating the catalogs for a customer who wanted to expand their disk space for their XenApp workloads. As you probably might know, the only way to expand the C drive space is by recreating the machine catalog.
XenApp version is 7.15 LTSR which was deployed originally as XenApp 7.5 and later upgraded to 7.15 LTSR version meaning that the original catalogs weren’t created using MCSIO.
The catalogs that needed Citrix MCSIO turned ON didn’t have the disk cache feature alive in the Catalog creation wizard. See the picture below.
Citrix MCSIO was first introduced in XenApp 7.9 which was supposed to be an alternative to PVS’s own memory cache feature. It is still debatable that if MCS’s memory cache feature is as good as PVS, but admins these days have an alternative if they want to give their workloads a bit of performance boost while running MCS.
Now, back to the issue! The fix lies in the Hosting Node in Studio where you have/had configured the connection to your hypervisor. In my case, when they were originally created, there was no MCSIO feature around so never had storage options to turn ON back then.
You could either edit the existing Resources under existing Connections.
I chose to create a new Resource under an existing Connection.
You will basically need to choose a Cluster in your hypervisor farm and choose between Local and Shared storage.
Under Storage Selection, select the datastores for OS, PvD and Temporary Cache. Though PvD is deprecated, it doesnt let you progress unless PvD option is ticked.
Choose a Name for your Resource and select the Network Adapter.
Click Finish at the Summary page.
Note – if your MCSIO driver version is older than 184.108.40.206, you will most likely have performance issues. I am running XenApp 7.15 LTSR CU3 which already has the above driver version.
Once you have setup your new Resource under Hosting node, head over to the Machine Catalog node in Studio.
Create a new Machine Catalog and you will see that the Disk Cache option is alive.
Microsoft Windows Virtual Desktops (WVD) has been making a lot of waves in the EUC industry ever since it was announced by Microsoft in September 2018.
Windows Virtual Desktop (WVD) is a desktop and application virtualization solution that runs from Microsoft Azure. Unlike, Microsoft’s previous foray into the application and desktop virtualization markets in the past with Microsoft RemoteApps which didn’t take off quite well, this time I believe they have a compelling product in their hands.
WVD provides an impressive list of things to the companies who want to adopt it. The important benefits are quoted below.
Set up a multi-session Windows 10 deployment that delivers a full Windows 10 with scalability
Virtualize Office 365 ProPlus and optimize it to run in multi-user virtual scenarios
Provide Windows 7 virtual desktops with free Extended Security Updates – This is big for a lot of companies around the world who aren’t ready to migrate to Windows 10 yet.
Bring your existing Remote Desktop Services (RDS) and Windows Server desktops and apps to any computer
Virtualize both desktops and apps
Manage Windows 10, Windows Server, and Windows 7 desktops and apps with a unified management experience
Below are the licensing requirements for running WVD in Azure.
Your infrastructure should meet the following requirements to support Windows Virtual Desktop:
So, what is Citrix doing here and how does Citrix add value to the WVD offering? WVD by itself is a perfect fit for a lot of businesses out there, mostly the start-ups and SMBs. What if we combine WVD with Citrix? That’s a deadly combo right there. Citrix could take Microsoft’s WVD offering to the next level by wrapping a management layer around it, offering flexibility, choice, cost optimization and enhanced security.
The enhancements that Citrix provide to WVD offering is best depicted in the picture below (courtesy of Citrix).
Citrix has developed special optimization packs for Microsoft Teams and Skype for Business which makes a world of difference, if businesses want to run these collaboration tools in a virtualized infrastructure. Without the optimization packs, it’s virtually impossible to deliver good user experience with Teams and Skype for Business when using Audio, Video and Screen Sharing. Running single-session VDI workloads still won’t cut it either.
Hybrid Cloud Model – WVD would only lets you run your multi-session Win 10 workloads in Azure. Citrix could further compliment that approach to run your traditional RDSH workload wherever you would like – on-prem, Azure, AWS, Google Cloud, Oracle Cloud or on HCI solutions such as Nutanix. Customers can combine WVD with RDSH workloads and manage them via a single console.
Use Citrix HDX which is the best of the breed in remoting protocols.
Citrix Machine Creation Services (MCS) lets rapid creation of virtual machines with minimal infrastructure utilizing the hypervisor APIs.
AutoScale – Customers could quickly ramp up and down workloads on-demand. These days, customers have an option of doing vertical load balancing which brokers user load/sessions to a single machine until a desired level is reached after which the connection gets routed to the next workload until it gets fully loaded. This is so much useful in cost optimization and reduces the overall Total Cost of Ownership (TCO) by reducing the numbers of extra servers used.
Advanced Monitoring – Citrix has its own repertoire of monitoring tools on top of Microsoft’s Azure-based monitoring.
App Layering – Citrix App Layering radically reduces the time it takes to manage Windows applications and images. It separates the management of your OS and apps from your infrastructure. You can install each app and OS patch once, update the associated templates, and redeploy your images.
App Protection is an add-on feature that provides enhanced security when using Citrix Virtual Apps and Desktops published resources.
Session Recording allows you to record the on-screen activity of any user session hosted on a VDA for Server OS or Desktop OS, over any type of connection, subject to corporate policy and regulatory compliance. Session Recording records, catalogs, and archives sessions for retrieval and playback.
Citrix Analytics – AI driven performance and security analytics to businesses that deploys Virtual apps and desktops service.
Citrix SD-WAN – Citrix SD-WAN is a next-generation WAN Edge solution that simplifies digital transformation for enterprises. It offers comprehensive security, the best application experience for SaaS, cloud, and virtual apps and desktops.
With Citrix and WVD combo, customers can bring the multi-factor authentication vendor of their choice such as Okta, OAuth-based authentication, RADIUS-based multi-factor auth and so on.
Let’s Bust a Myth
This may come as a surprise for many of you who are working in the EUC space. A lot of the folks in the industry are thinking that in order to use WVD, you will need to buy Citrix Managed Desktops which is new product offering from Citrix and that is the only offering entitled to use WVD. That isn’t true at all.
You could use a plethora of the following services from Citrix and enjoy the full benefits and simplicity that WVD has to offer. In summary, if you are an existing Citrix Cloud customer that utilizes any of the below services from Citrix, you are entitled to WVD as well.
Let’s conclude this. Citrix’s offering isn’t really trying to compete with Microsoft’s WVD, but rather they are complementing each other by providing more choices to the customers who want to run their VDI and RDSH workloads in the cloud. Isn’t it great to have choices in life? 🙂
If you have noticed the Restart button for published desktops in Citrix Virtual Apps and Desktops 7 1912 LTSR recently and wondered why in the world Citrix would give users access to users to restart machines, you are not alone. Make no mistake, this is a perfectly fine setting to be enabled out-of-the-box for VDI deployments where just Desktop OSes are being published or on the delivery group that contains Desktop OSes. You would want your users to be able to restart the desktop every now and then anyway.
Now after going through the Citrix SDK documentation, I found the below notes for the -AllowRestart argument that governs the restart button.
AllowRestart (System.Boolean) Indicates if the user can restart sessions delivered from the rule’s desktop group. Session restart is handled as follows: For sessions on single-session power-managed machines, the machine is powered off, and a new session launch request made; for sessions on multi-session machines, a logoff request is issued to the session, and a new session launch request made; otherwise the property is ignored.
So, it isn’t too bad to have that button available for RDSH delivery groups but should probably be called something else. The name “restart” has a negative vibe to it in multi-session world. lol
The option\button will appear like the below.
How would you remove the Restart option?
You will need to do this via Powershell.
Find the delivery group that has RDSH based published desktops and take a note of the Name parameter. You can do this on all the delivery groups if you want to disable this button for all published desktops, both RDSH and VDI.
Run the below command to find the value for the delivery group that you want to turn OFF the setting for. The parameter we are looking for is AllowRestart. When the value is True, Restart button is shown. Setting it to False will remove the button from Storefront.
Citrix Machine Creation Services (MCS) is a compelling technology these days for provisioning virtual machines quickly and easily in Citrix environments. The whole technology is built around simplicity and requires just a supported hypervisor that utilizes snapshots to create additional VMs on the fly. There isn’t much required from a supporting infrastructure point of view as well. If you have a robust hypervisor with enough space in the storage array, MCS will work just fine. All that you would require is a service account with defined permissions for the whole thing to function.
If anyone wants to know what permissions are required for the MCS service account to function correctly, that could be found in the following Citrix official links.
I will even argue that MCS is just as good as another provisioning technology from Citrix, named Citrix Provisioning (formerly Citrix Provisioning Services or PVS) with the recent advancements it has made. There are scenarios when Citrix PVS is the better choice but that is a topic for another blog post.
While we are in the midst of Coronavirus pandemic and everyone is staying at home safe and sound, I have had some pleasant experiences working with MCS spinning up extra virtual machines for my customers here in Auckland, as they needed to ramp up their farm capacity to cater to the extra load. I could literally spin up machines in seconds(I am not exaggerating even a bit…) and just be ready for the incoming wave of Citrix users.
In this blog, let’s discuss how Citrix MCS works in general and what happens under the hood when MCS creates virtual machines. Let’s also discuss and compare Citrix MCS in an On-Prem setup versus MCS in Azure. I also have to say that most of the diagrams that you see below are shameless copies of Citrix’s own diagrams used in one of their webinars. I don’t mind accepting that 🙂 Now, that’s out of the way, let’s dive right in.
Citrix MCS – On Prem
So how does Citrix MCS works with your On-Prem hypervisor?
You create a master template or gold template and make all the changes that you want to it.
Once you are happy with the changes to the VM, go to your hypervisor console and take a snapshot of the VM.
After that you go to the Studio console and either add a new Machine catalog or add machines to an existing catalog. At that time, a full copy of the VM’s base image disk is taken and copied to the first storage repository (Datastore for VMware folks!).
Now it creates a Preparation VM and it is going to get interesting from now on.
To the Preparation VM, an Instruction Disk is attached. This will strip out all the previous identity information from the prep VM. In other words, it de-personalize the VM so that a fresh identity could be assigned to it at a later stage.
Now its time to power ON the Preparation VM.
The Image preparation process begins in step 7.
The Preparation VM now updates the snapshot A’ along with the original snapshot.
The Preparation VM is shutdown after this stage.
The Instruction Disk is deleted.
The OS disk is detached and the preparation VM is also deleted.
The update snapshot A” is now replicated to each storage repository(or Datastores in VMware). The image is now ready to deploy.
MCS now creates copies of that image and in that process creates Identity Disks that differentiates the VM from others. If you create more than one VM in the Machine catalog, more Identity Disks are created and will assigned to each image.
Next step is creating the required number of VMs by attaching the Identity Disks and Differencing Disk. Since all the VMs are sharing a single snapshot, the snapshot is read-only. Any changes, additions or runtime area is added to the Differencing Disk. The on-prem hypervisor is now leveraged to merge the disks to produce the virtual machines.
Identity Disks are 16 MB in size and are read-write capable. This makes them reusable for future VM creation. Delivery Controllers are responsible for creating Identity Disks.
Citrix MCS – Azure
Now let’s look at how MCS works in Azure. It’s mostly the same steps except for a few key differences. In the on-prem version, depending on the hypervisor used, the file formats could vary as in VMDK for VMware vSphere and VHD for Hyper-V or Citrix Hypervisor. With MCS in Azure, the disk file format is VHD as it is based on Azure Hypervisor which is a customized version of Hyper-V.
You create a Master VM to make further copies of it just as in traditional MCS setup.
The Master VHD is created in a Storage Account. This is the master storage account.
We then run the MCS Wizard via the Studio if you use the Citrix Cloud service or from Azure Portal if you are subscribed to Citrix Virtual Apps and Desktops Essentials.
The MCS Wizard checks for the availability of the resources using the Azure API.
We will now create a Resource Group (RG) to host all the additional VMs that MCS will create in Azure. One RG could host upto 240 VMs.
Storage Accounts are created within the Resource Group to host the disks for the virtual machines. One storage account can host up to 40 VMs. Additional storage accounts are created depending on how many VMs we need.
Network security Groups (NSG) are created next and they will isolate the prepped VM from the rest of the network. If we need 400 VMs, two RGs will be created to host all the VMs.
Next step is validate the connections. The Service principal connectivity will be validated to access the Azure resources.
The image is consolidated and is prepared for copy. Remember the image is located in the Master storage account in the steps above.
The Master Image is copied to the other Storage accounts defined for the machine catalogs. Unlike other hypervisor approaches, we don’t need to create snapshots ourselves in this occasion. Azure based Citrix MCS will use the provisioning APIs in Azure to set this all up for us.
The Identity disk for the Preparation VM is created but not attached yet.
Preparation VM (A’) is created after that.
Once the Prep VM is ready, it is stopped to attach the Identity Disk.
At this stage, the Identity Disk is attached to the Preparation VM.
The Preparation VM is started again for further steps.
Once the preparation steps are completed, the VM is stopped.
Preparation VM disk is now copied to the new Storage Account that is defined for MCS. This is the Base Image.
The base image is replicated to other storage accounts within MCS.
The Preparation VM and its’ Identity Disk is now deleted.
Then we have a Pre-Flight check where all the created resources are checked for its integrity by MCS. Now the Base Image ready to be cloned to make more VMs.
Storage Accounts – Legacy Approach
Now, there are two approaches here – Storage Accounts (Legacy ) and On-Demand Provisioning. Let’s discuss Legacy approach until steps 21 to 25.
Identity Disks are created for the required number of VMs that will be created by MCS.
OS Disks (from Base Image) are also created followed by Identity Disks.
VM are provisioned and linked to the OS Disks.
Identity Disks are attached to the VMs.
VMs are stopped to avoid extra costs during billing. (This is the case of VDI machines). When users connect, the machines are started on-demand and VMs are fired up ready for action.
In On-Demand provisioning method, MCS will keep all the required settings within the database and will create VMs only when it is required in an on-demand fashion and not pre-created as in traditional MCS.
Only identity Disks and NICs are created during MCS in this approach.
You would have noticed by now, instead of Storage Accounts, Azure Managed Disks are being used here.
When there is user traffic in the farm, Citrix VDAs are created on-demand. As a part of that step, OS Disk is created at VM launch time.
VMs are created and linked to the OS Disks at VM launch time.
As a final step, Identity Disks are attached to the VM at launch time before the VM is ready to serve the users.
Once the VM is no longer needed, the VM is shutdown and deleted.
OS Disks are also deleted post shutdown.
However, the Identity Disks and NICs are retained for future use. When the VMs are required again, the OS Disk will be attached, merged with the Identity Disk before it is available to be used again.
That’s about it peeps. Happy MCSing in the cloud!!
If you have implemented DirectAccess for your users so that they could connect to corporate network whilst they work from home, you might have come across this issue while using Citrix. Users would be able to connect to Storefront portal and authenticate themselves but when they try to launch applications it fail. Users will also notice the below Citrix Receiver dialog with no apparent error messages.
The users who connect directly to Storefront without DirectAccess have no issues to launch applications.
When you have DirectAccess enabled on user PCs, it expects hostname/FQDN values for initiating traffic between the client and the DA gateway. By default, Citrix XenApp tries to connect on IP addresses to bypass the infrastructure reliance on DNS. So, we will need to find a way to switch that behaviour to an FQDN based connection initiation.
Let’s look at the .ICA files to see what’s in there. The below screenshot is of an ICA file that shows IP addresses. This setup will NOT work for DirectAccess connections.
To fix this, you will need to change a DNS parameter in XenApp/XenDesktop 7.x farms.
You will need to change the value from False to True
Set-BrokerSite -DnsResolutionEnabled $True
Running a Get-BrokerSite after that will show that the value has been changed from False to True
Now, let’s inspect the ICA file again. You can find the ICA files from your User profile folder. I had mine under