5 Replies Latest reply on Oct 11, 2011 11:04 AM by kunhuang1980


    Jessicas Dad Novice





      I need a little help.  I configuring ESX for iSCSI.   I have configured one vSwitch with four uplinks and a vmkernel port.  I would like to load balance the iscsi traffic across these four uplinks. Is this possible.  We have 4 iscsi target serving out all luns from the storeage.















        • 1. Re: iSCSI
          weinstein5 Guru

          Not in the true sense - what you can do is set the load balancing in the switch configuration to IP Hash - The vmkernel will then select the outbound physical NIC for each packet based on the originating IP address and destination IP packet but not knowing the algorithm used I can not say all four nics will be used - also not you will have to some form of link aggregation like ether channel configured on the physical switch you connect to -





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          • 2. Re: iSCSI
            Jessicas Dad Novice


            The only way that I can provide either channel is to provide one iscsi target presenting all luns to all servers.  The limitation I see with this is, as you have only one iscsi target ip address all traffic will be transmitted on one uplink port on the vSwitch?  Is this correct?  Is it the case even though you have given the iscsi software initiator mutiple targets all comunication between the luns and the iscsi initatior will take place on a single initiator?






            Many Thanks





















            • 3. Re: iSCSI
              weinstein5 Guru

              That is correct - with only one IP target then yes you would only use a single physical NIC





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              • 4. Re: iSCSI
                jjkrueger Expert
                VMware Employees

                The software iSCSI initiator in ESX is a single instance - you cannot configure multiple software initiators.


                Each iSCSI target (in the context of ESX, we will refer to a storage processor or iSCSI server as a target) may have multiple LUNs hanging from it, but will typically have a single IP address.


                If you have multiple iSCSI targets, you may get some benefit out of using the IP-based vSwitch load balancing method.  You would want to look at how many targets you have, and base the number of uplinks around that.  In other words, if you have 2 targets, each with a unique IP address, you would want two NICs.  Perhaps three, if you want additional redundancy, and you want to maintain pre-failure levels of performance.


                If you have a single iSCSI target, there is no need to add to the complexity of the design with any load balancing method other than the default vSwitch port-ID based method.  Here, two NICs for uplinks would be more than enough, as you would only use one of them at a time.


                The software iSCSI initiator is just a software stack in the VMkernel.  This software stack will communicate with the IP network just like any other application running in the VMkernel - through a VMkernel port, which is in turn attached to a vSwitch.  Using the software iSCSI initiator binds your storage traffic to all of the design considerations of the ESX virtual networking stack. 


                Hope that makes sense,