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It's common for virtual desktop environments to experience performance issues, but there are ways to prevent them.
IT admins should be aware of several tips to prevent and eliminate Citrix performance issues, including how to properly configure provisioning services and cache mode in Citrix Virtual Apps and Desktops.
One way to prevent Citrix performance issues is to optimize the OS. Out of the box, Windows 10 is not designed to run as a virtual desktop OS; it is built to run on laptops, PCs and tablets. Microsoft includes a lot of services such as wireless LAN services, diagnostic settings and cleaning scheduled tasks that are unnecessary for using Windows 10 as a virtual desktop OS.
IT can disable these services and optimize the settings to give the image a significant performance boost. When creating a new virtual environment, IT should optimize the OS by downloading and running Citrix Optimizer. This tool comes with built-in templates and is fully supported by Citrix. If IT admins are already running an existing deployment, then they can run the tool in a scanning mode to optimize missed settings.
Provisioning services configuration
One of the most common performance issues with nonpersistent Citrix environments is a misconfigured Citrix Provisioning Services (PVS) environment. To get the most out of PVS, IT should first correctly size the RAM of the PVS server. Citrix PVS will cache the reads of the vDisk in the RAM. This way, the next VM that boots from the same vDisk reads from the RAM of the PVS server, which is much faster than the disk. Citrix offers a guide on sizing the RAM and provides an easy equation to calculate the right amount of RAM:
2GB + (#XA_vDisk * 4GB) + (#XD_vDisk * 2GB) + 15% (Buffer)
Another issue that causes performance degradation is PVS versioning. IT should not have too many versions on top of the disk and merge the versions instead. If possible, IT should try to avoid using versions completely. IT can automate the complete vDisk creation process to eliminate the need for versions. If IT admins need to make a change in the disk, they can edit it in the automation process and create a new vDisk without creating a new version.
IT should use the cache mode correctly to prevent Citrix performance issues. Oftentimes, the cache of Citrix VDAs is completely full, because after IT boots the machine, software is installed via automation or Group Policy. All of these installations end up in the cache, because the machine runs nonpersistent. Often, IT configures cache in RAM with overflow on hard disk, and the RAM is full with software installations, which is expensive storage for installation and causes performance degradations.
More Citrix performance tips
App-V shared content mode
When using App-V with nonpersistent Citrix machines like PVS or Machine Creation Services, IT should configure App-V to use shared content mode. This way, App-V will not download the complete packages and fill up the cache.
Use performance monitoring software
The easiest way to identify Citrix performance issues is to use performance monitoring tools such as ControlUp, Liquidware Stratusphere or Uberagent.
Machine Creation Services fast storage
Machine Creation Services (MCS) uses storage to clone nonpersistent VMs. The faster the storage is, the faster the VMs boot and load programs. IT should use MCS with solid-state drives -- or, even better, non-volatile memory express SSDs.
Virus scan whitelist
It is very important to properly configure the virus scanner in a Citrix environment, which can give a performance boost. IT should follow Citrix's written guidelines for antivirus software.
When using XenServer in combination with PVS, IT should check out PVS accelerator. This will cache the vDisk in the RAM of the XenServer Hypervisor and make the disk reads blazing fast.
IT should make a new version of the vDisk with the installations in it, rather than add it to booted machines. The default size is 4 MB when Citrix creates a cache file on the persistent disk. If a cache file is much larger than a few hundred megabytes, there might be something wrong that degrades performance.
IT should redirect to the persistent disk such as the printer spooler, event logs and WEM cache. The free Base Image Script Framework tool can help with this.