Network performance issue between XenServer and HP Blade

We came across very interesting performance issue on XenServer installed on HP Blade with Flex Fabric (Virtual Connect).

By default VC switch configured as default STP (Spanning Tree Protocol) . While uplinking virtual connect to the core switch , make sure that core switch port is configured for same STP . In our observation we found that core switch port were configured for MSPT (Multiple Spanning Tree Protocol) and link aggregation (LACP) were configured using 1GB port.

Due to STP configuration changes , convergence were talking some additional time. This results in  RTO and packet drop which was causing XenApp session freeze.

Conclusion : If LACP is used to get 4GB thoughput on uplink , make sure that there are no protocol mismatch. Default protocol on VC can be changed to match core switch protocol.