11 Replies Latest reply on May 21, 2019 8:06 PM by nuampat

    vmxnet3 adapter on windows server 2012 with MSSQL server bottleneck problem

    vadonka Lurker



      We have a windows server 2012 R2 with MSSQL server 2014.

      The client software is using jdbc connection to the database. If the clients perform a query what is collecting massive amount of data the whole thing is slowed down after a while.

      Then its need to wait 10-20 min to speed up again. I tested everything and tried everything,

      - measured the ethernet endpoints

      - replaced the cables with cat7

      - installed a virtual machine with windows client and the real client use the virtual enviroment via rdp

      - enabled the RSS in the vmxnet3 advanced settings and in the windows

      - enabled SplitRx mode in the vcenter vm settings and disabled ethernet coalescing too

      - set the vm to high latency

      - tried to migrate the vm to another host


      Non of them help. If a massive sql query is running first its running great, then its need a second or more to check one record.

      checked the vm cpu stress but its under 5% all the time. Checked the network with wireshark, there is many small packages but nothing big. The used bandwidth is remain low.

      When its slowed down the delay after two packages will increase from few ms to 400-500ms.


      Our strongest server is a HP DL380 G9 with two octa core Xeon cpu and 384GB ram, full SSD datastore. Its a lightning fast host.

      The vm have 8 cpu core and 64GB ram.


      No matter where am i place the vm or how much resources give the issue wont gone.

      The strange thing is when the clients slowed down i can copy big files between the client and the server with fast speed, so only the sql slowed down.


      I can resolved this issue if i use the E1000 ethernet adapter instead of the VMXNET3, but E1000 have much more overhead, and the server need to transfer bigger files too not just serve the sql.

      VMXNET3 much more faster and have lower overhead but with this sql issue i have a problem with that. So i revert to the E1000 for now. Its slower eat more cpu but the sql connections working fine without any problem.


      Anybody can point me what can i do more to identify the vmxnet3 issue? I really need that for better network performance and lower overhead, but the fast sql is the top priority.


      Thanks! !