Creating and Configuring an iSCSI Distributed Switch for VMware Multipathing

In an earlier post I configured my Synology DS1513+ Storage server for iSCSI and enabled it for Multi-Pathing, in this post I will show you how to create and configure a vDS (vSphere Distributed Switch) for iSCSI use and how to enable Multipathing to use more than one network path to your storage (there by increasing throughput).

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Using the vCenter client you can see that in the above screenshot that I have 4 Intel NIC ports on my hosts that aren’t currently assigned to a vswitch.

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Click on Inventory \ Networking \ Add a vSphere Distributed Switch

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As this is a vSphere 5.5 lab I went for the 5.5.0 version switch, click Next

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For ease of management I have named my switch iSCSI, click Next

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Select the NIC’s from each host to add to the switch, click Next

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Un-tick the Automatically create a default port group as we are going to add these next, click Finish

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Right click your new switch and choose New Port Group

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We are going to create 4 new Port Groups, I have gone for 3 ports per Port Group because I only have 3 hosts. Name your Port Group (in this case iSCSI-1) and define the number of ports, click Next

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Click Finish, now repeat for every new port group required.

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Here we can see that I now have 4 different Port Groups configured.

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Right click iSCSI-1 and click Edit Settings

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Click the Teaming and Failover setting, we can see that currently all 4 uplinks are active, for iSCSI use you’re going to need to have only a single active uplink.

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Because this is iSCSI-1 I am using uplink 1 to be the active uplink, move the rest of the uplinks to Unused Uplinks

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Here are the iSCSI-2 settings, I have used uplink 2 as the active uplink.

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Here are the iSCSI-3 settings, I have used uplink 3 as the active uplink.

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Here are the iSCSI-4 settings, I have used uplink 4 as the active uplink.

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Go to Hosts and Clusters and click on your host, browse to Configuration and Networking, click on Manage Virtual Adapters

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Click Add

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Choose New virtual adapter, click Next

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Click Next

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Select the required port group (iSCSI-1) and click Next

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The Hosts IP address is 192.168.2.30, because I have used the 192.168.5.x network for my iSCSI traffic (on a dedicated switch) I went with 192.168.5.31 for this NIC’s first IP, click Next.

Repeat for the remaining adapters.

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In this screenshot you can see all 4 adapters added.

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Clicking each Port Group we can see that each one is linked to an individual Uplink as mentioned previously.

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Going back to Inventory \ Networking we can see the Networks tab.

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Here is the Inventory \ Networking\ Configuration tab showing the whole config.

Go back to the Inventory \ Hosts and Clusters \ Configuration \ Storage Adapters screen

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Click the iSCSI Software Adapter, if it’s not present simply click the Add button on the top right of the screen to add the iSCSI Software Adapter.

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You can see here that we have a single path configured to our storage (it’s currently using the LAN port group for connectivity), click Properties from the lower pane to bring up the iSCSI Initiator properties.

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Click Network Configuration

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Now we need to add the new Port Groups, Click Add

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Add each required port group individually. Once all 4 have been added remove the LAN port group.

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We now have 4 port groups added to the iSCSI Initiator, click the Dynamic Discovery tab

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Add the IP or Host name for your iSCSI storage (in the previous post I configured my Synology with 3 address in the 192.168.5.x network range), click on the Static Discovery tab and remove any unrequired entries there. Click Close

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Click Yes

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We now have 12 paths to the iSCSI Storage server but we would only be using a single path back to our storage so we need to change our Path Selection setting from MRU (Most Recently Used) to Round Robin.

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Right click the LUN and choose Manage Paths…

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Change the Path Selection to Round Robin, it’s worth pointing out that currently the Status for each path is Active but only a single path would be used for issuing I/O to the LUN

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Changing to Round Robin has made all of the Paths Active and all of them are now being used to issue I/O to the LUN.

Repeat the above steps on all hosts.

It’s worth noting at this time that by default the Path Selection Policy (PSP) will send down 1000 I/O’s before moving on to the next path, in a busy Production environment that’s not much of an issue but if you’re using this in a home lab you may want to reduce this down to a single I/O per path. If you want to go down that route please have a look at Cormac Hogan’s site here for instructions on how to configure that.

2 Comments

  1. Sweet post. I am trying to get as much information to show them that going to VDS is the way when using ISCSI storage. So one question, if a NIC on a single host that is supporting ISCSI goes out will a VDS send the traffic out another host connection because we have a NIC from each physical host in the DVUplink? I think I know the answer but thought I would ask you to get the correct answer.

    • Hi Mitch, as long as you have multipathing configured correctly with multiple uplinks then you’re good to go, single nic then it’s a single point of failure. Multipathing is your friend.

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