Hyper-V hardware / system performance issues

Hi:

Are there any specific BIOS settings for Hyper- V that we should take into account when reinstalling a PowerEdge R620 with Windows Server 2012 Std to virtualize 8 virtual machines with Windows Server 2008 R2? I detail more our problem if anyone can help with any other ideas :

We have a Hyper- V cluster of two nodes with two PowerEdge R620 and one PowerVault MD3200 with dual controller. The connection between the servers and the SAN is via two dedicated 6Gbps SAS HBA in each server (one HBA on each server to each of the controllers). Physical operating systems are Windows Server 2012 Std and virtual operating systemas are Windows Server 2008 R2 Std.

From the beginning we had performance problems with virtualized applications (proprietary databases). We assumed it was something related to the SAN or to the storage access. After many changes and testing we have ensured that the disk subsystem is not a problem, and performance has greatly improved, but some problems remain the same, and one of them especially.

Anyway, tired of trying , testing , configuring ... we have mounted the main application virtual server, where more marked is the problem, into an old HP server ( almost 5 years) installed also with Windows Server 2012 Std, and surprise, the problem disappears. We repeated the procees in another HP outdated server, and again OK. Further tests are consistent, and that the new hardware performance in processor and disk access are much worse than the current system, as expected.

The obvious conclusion is that there is some problem on Dell servers, and in the two servers (since the virtual machine directly executed on both, without cluster and without SAN, exactly reproduces the problem ), which leads us to think of a problem with the physical operating system installation (both servers have the default Dell factory installation), BIOS parameterization, or some component firmware.

The specific problem is a process that runs locally on the application server, not using network communication, but using hundreds of thousands of sockets open from the server with himself. Spying the process with a sockets sniffer we can see how the socket opening speed are slowing as the number of sockets grows. In the standard test the application virtualized on a R620 takes about 4 and a half minutes to complete the process, and exactly the same time using SAS HDs in the SAN, or even local SATA HDs or local SSD HDs. Simply changing to the old HP machine with a local SATA storage the process takes only 1 minute and 30 seconds.

Any help is welcome. Thanks in advance.