We are facing a strange behaviour of our virtual servers on Cisco UCS Blade with Fabric Interconnect 6100.
- when we place the virtual server on a HP-standalone server (with ESX) we are facing proper performance (even if connectio n speed is only 1Gig)
- When we move the virtual server on Cisco UCS (where we have 10Gig connection) we have 1/10th of performance
the performance is overall good as long as we stay within the LAN (low delay). as soon as we copy via WAN (10Gig connection with a RTT of approx. 7msec) we are facing this big differences between virtual server on old HP and new UCS,
we had a look into the traces and we see that the virtual server on Cisco UCS is not able to use the whole tcp window. during the tcp handshake a window scaling factor is negotiated but during the copy it seems that it is not able to use it (the server is able to use max. 16060 bytes that are unacknowledged). as soon as this windows is full he has to wait for 7msec for the acknowledge.
any ideas why this can happn on UCS and what we could change??
thx
