Citrix VDI VM’s freezing intermittently

While testing a new Windows 10 VDI environment we came across the following issue: The VM’s started freezing intermittently. The issue started after migrating a large group of users to the environment. We hadn’t had any issues beforehand and no recent changes where made to both the infrastructure and the PVS vDisk. VM’s where completely frozen, so the eventlog was no help and showed a gap from the start of the freeze until the reboot of the VM.

It took a while to find the answer and since it was not easy to find (a small footnote in CTX138933) I thought it best to write this blogpost. The problem was that in PVS the vDisk Load Balancing configuration was configured for both Subnet Affinity and Rebalancing:

If your configuration matches the picture above you have to uncheck Rebalance Enabled. Subnet Affinity does it’s own rebalancing so if you leave both options enabled they will continously rebalance connections until the streaming service fails and the whole thing falls apart.

We started using Subnet Affinity after migrating some servers to another datacenter. Before we migrated the users there wheren’t enough sessions/connections to cause any problems.

Michaja van der Zouwen

Is an all-round IT engineer with special skills in Microsoft, Citrix, RES and VMware products. Loves a challenge in his work and has taught himself scripting. Initially batch scripts, and later PowerShell. This helps him to automate processes and procedures, and to develop his own management tools which can be used every day.

Core qualities
Team player, enthusiastic, eager to learn, sociable, positive

Hobbies
Football, playing music, watching movies and series

Job description
Senior Technical Specialist