Question about Route Based on IP Hash

[76dragon]

If a network switch is setup to aggregate 2 x NICS configured in a port group with 2 x vmnic's for NFS storage, Does vSphere automatically load balance across the aggregated links or does I actually need to tick the load balancing box and manually specify the load balancing option of "Route based on IP hash"

Anyone know if this just works out of the box, or if the check box ticked is needed ?

Thanks

[JaySMX]

Out of the box, ESX does not support active link aggregation (LACP). The caveat is when you are using the Nexus 1000 switch, which does support it. Take a look at this link:

http://virtualgeek.typepad.com/virtual_geek/2009/06/a-multivendor-post-to-help-our-mutual-nfs-custom...

It gives you a great rundown of how NFS works within VMware. Essentially NFS traffic to a single target will be routed down a single link due to it utilizing a single TCP connection. This blurb in particular talks to your question:

"Ok – next thing to understand is that every NFS datastore mounted by ESX (including vSphere – though NetApp and EMC are both collaborating for longer term NFS client improvements in the vmkernel) uses two TCP sessions – one for NFS control information, and the other for NFS data flow itself.

This means that the vast majority of the traffic to a single NFS datastore will use a single TCP session. What this means is that the upper limit throughput achievable for a single datastore – regardless of link aggregation or other methods – will use a single link for the traffic to that datastore."

-Justin

[weinstein5]

By default the Load Balancing Method is set to Route Based on Virtual port - this is the one selected because it will work with all physical switches and does not require LACP - you will need to enable the Route Based on IP Hash to take advantage of LACP -

Also please keep in mind vsphere does not truly load balance - a better description is load distribution - for instance with IP Hash vmkernel chooses a physical NIC based on the originating and destination IP address - so if you are going to use IP Hash to connect to a NFS datastore with a single IP address traffic will only exit a single physical NIC to the target NAS/NFS datastore -

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