When running Sophos Anti-Virus with the on-access scanner enabled on a Citrix Server there is a degredation in performance as the number of endpoint computers connecting to the server increases.
The CPU usage for the SAVservice.exe process will spike and only a small number of computers will be able to connect to the server e.g., 15-25 clients.
First seen in
Sophos Anti-Virus for Windows 2000+ 9.0.5
On-access exclusions have not be implemented correctly.
What To Do
Configure on-access scanning exclusions as recommend by Citrix. See article 35970 for more information.
If you believe all exclusions to be in place see article 13045.