Microsoft Virtualization Discussions

Flow Control - ISCSI 10Gb VIF to 1GB Hosts?


I am doing an implementation of a hyper-v and a SQL cluster attached to a FAS2240 10GB VIF that will be using ISCSI for LUN to Windows 2008 R2 hosts. The servers themselves will be connecting at 1GB to a pair Nexus2Ks. I am trying to see if there is a NetApp recommendation on Flow Control settings for Hyper-V/Windows servers for ISCSI in this scenario similar to the VMware recommendation on Flow Control in TR-3749.

In TR-3749 it states “FLOW CONTROL

Flow control is a low-level process for managing the rate of data transmission between two nodes to prevent a fast sender from overrunning a slow receiver. Flow control can be configured on ESX/ESXi servers, FAS storage arrays, and network switches. For modern network equipment, especially 10GbE equipment, NetApp recommends turning off flow control and allowing congestion management to be performed higher in the network stack. For older equipment, typically GbE with smaller buffers and weaker buffer management, NetApp recommends configuring the endpoints, ESX servers, and NetApp arrays with the flow control set to "send."”

Does this still apply in a scenario where the NetApp is connecting to a switch at 10GB, with Windows 2008 Rs Servers connected at 1GB for ISCSI? Is there a definitive recommendation or best practice?

Thanks in advance.




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