31 December 2016

Poor Network Performance | Network Shares (Server 2012 R2)

I was recently doing some work for a client where they had noticed that the network performance from their workstations to the File Server was rather poor.  When transferring data to the File Servers (and any other shares on the Virtual Host), it was very slow.

All the VMs were either Server 2016 or 2012 R2, and it was running on a Virtual Host which was Server 2012 R2.  The Server was a Lenovo x3650 m5.  All the NICs were Broadcom and the drivers were fully up to date.

After looking into the issue, I found that some of the settings on the Network Adapters needed to be changed/updated (on the Virtual Host itself) to allow for faster transfer speeds.  To do this, I needed to open up each Network Adapter, then click on Configure, then the Advanced tab.  Once I did this, I had to set the following options to Disabled:
  • TCP/UDP Checksum Offload (IPv4)
  • TCP/UDP Checksum Offload (IPv6)
  • Large Send Offload V2 (IPv4)
  • Large Send Offload V2 (IPv6)
  • Virtual Machine Queues
Just remember that when performing these changes, it will drop the network connectivity to the adapter for about 5 seconds.  If you're making this change on a live host, it will potentially disrupt network traffic to the VMs and the Host.  If you have a NIC Team in place, do this to one Adapter, then wait for it to come back online before doing it to the next one to make sure that network connectivity to the host itself remains active. 

After doing this to the NICs in my NIC Team, I tested the network connectivity and it was considerably faster.

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