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My question relates to iSCSI connections and VLANing.

My configuration is 2 Hyper-V hosts connected through a pair of stacked layer3 Dell 6224 24 port switches to an Equallogic PS4000 Storage Subsystem. The Equallogic has 2 iSCSI connections, active and pasive. All traffic - Ethernet and iSCSI - is in the same broadcast domain.

I want to isolate the iSCSI traffic from the general network traffic using a VLAN. However, my concern is that if I put the iSCSI ports in a separate VLAN, the host servers will lose access to the storage.

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  • What switch do you have?
    – Zapto
    Jan 27 '12 at 18:17
  • The Hyper-V hosts would also need the appropriate VLAN setup to be able to communicate with the SAN. Additionally, you'll likely have to do some switch configuration. I've got a similar setup (EqualLogic SAN, Dell PowerConnect switches, bunch of hosts) and use VLANs to separate iSCSI traffic. Additionally, you may want to check if that model switch has "iSCSI traffic optimization". Basically the switch detects iSCSI flows, and gives that traffic higher priority.
    – Kendall
    Jan 27 '12 at 18:18
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Here's two possible ways to accomplish this:

  • separate NICs on the VM Host for the iSCSI traffic and other IP traffic

    • this provides maximum separation
    • configure the iSCSI NICs as access ports on the switch going to the iSCSI VLAN, move the Equallogic ports to the iSCSI VLAN and you're off and running.

  • combined NICs on the VM Host for both iSCSi and other IP traffic

    • cheapest solution
    • create a subinterface on the NICs for the iSCSI VLAN, enable trunking on the switch going to appropriate VLANs, move the Equallogic ports to the iSCSI VLAN

If you're concerned about mistakes or losing access to the service, just move one NIC at a time. You do have multipathing set up, right?

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  • +1 but I wouldn't even bother with the combined NICs option at all: if you can afford a SAN, you can purchase a dual NIC expansion card.
    – gravyface
    Jan 27 '12 at 19:54
  • Right, that's definitely the best thing to do. Sometimes it's not as easy (for example: blades with only two NICs and it's a bigger job to add more)
    – MikeyB
    Jan 27 '12 at 21:32
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The 6224 will have iSCSI optimization, but it will only enable jumbo frames, flow control, and disable storm control. The 5000 series will do all of that, but also provision those ports with a QoS profile that prioritizes iSCSI traffic in the egress queues. :)

As long as you change all of the ports in question to use the SAME vlan, and do not change them from access ports to trunk ports, you'll be fine. You can use the interface range command do this all fairly simultaneously, but I would quiesce or halt whatever is using the storage first. You can then use the 6224 to perform inter-vlan routing, be sure to add the ip routing statement to the main configuration, and beware that the gui turns on some very evil proxy arping. Use the CLI if at all possible.

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