XenServer: How to Build and Configure a Dedicated NFS Storage Bond

GodzukiFirst of all let me start this off by saying that there is a lot of information out there on how to setup a dedicated storage interface on XenServer. However, I was unable to find anything specifically related to bonding two unmanaged interfaces and use them for as a dedicated uplink, which is seems rather silly to me as why would you not want to have a highly redundant network connection to your NFS storage. I digress.

Anyway, the first thing you need to do is to ssh into one of your XenServer hosts. In my environment I am building out a three node cluster and I need to make sure that I am working specifically with the first host in the cluster. So….

First thing you need to do is change the network backend of your Xenserver from "openvswitch" to "Linux Bridge". You accompish this with the following command.

#xe-switch-network-backend bridge.

Now you will need to reboot. Note that you can check your network-backend mode at any time with the following command.

#cat /etc/xensource/network.conf

First get the uuid of the local xenserver host, use the hostname to do this.

  # xe host-list name-label=xen01

The command above will return the uuid of the server.

uuid ( RO): 4a9971f7-1e59-4e02-b849-04d206ee7b2b
name-label ( RW): xen01
name-description ( RW): Default install of XenServer

Then you need to get a list of pifs on the host that you are working with (making sure to exclude any other host's interfaces). The command below will output this list. We will need to grab the uuids of eth2 and eth3, since they are the interfaces that we are going to use to build our bond. Note that we are running this command so that it will spit out our MAC addresses as well… make sure that you take note of these as you will need them.

 #xe pif-list host-uuid=4a9971f7-1e59-4e02-b849-04d206ee7b2bparams=uuid,device,MAC,host-uuid

Next we will tell XenServer to "forget" or un-manage eth2. Then we will do the same to eth3. We will use the uuids of these interfaces to identify them to XenServer.

Example with interface eth2 in unmanaged mode. Rinse and repeat for eth3.

# xe pif-forget uuid=97afe085-c679-3aa0-d09b-3c530ee3ac60

Then list all PIFs to ensure the unmanaged one is no longer in the list:

# xe pif-list host-uuid=97afe085-c679-3aa0-d09b-3c530ee3ac60

If you have successfully removed them its time to start creating your bond.

First define your bond in /etc/modprobe.conf. I am calling my bond, bond51

alias bonding bond51
options bond51 miimon=100 mode=7

Then edit /etc/sysconfig/network-scripts/ifcfg-eth2 and /etc/sysconfig/network-scripts/ifcfg-eth3. Make them look like the file below. Change the device name for ifcfg-eth3 to eth3.

DEVICE=eth2
BOOTPROTO=none
HWADDR=<MAC ADDRESS OF YOUR INTERFACE>
ONBOOT=yes
MASTER=bond51
SLAVE=yes

Then create /etc/sysconfig/network-scripts/ifcfg-bond0

DEVICE=bond51
IPADDR=<YOUR IP>
NETMASK=<YOUR NETMASK>
ONBOOT=yes
BOOTPROTO=static

Beep Boop. Ifup bond51 to bring up the bond and its slave members.

You can check the status of the bond via the command below.

cat /proc/net/bonding/bond51

Please know that I have done little more than reboot the XenServer host to make sure that the configuration that I built would persist across reboots, and failover from one interface to another. I have not tested performance yet in any way shape or form.

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How to Create A Dedicated Storage NIC in XenServer

Wickenburg-networkIn Vmware ESX, when using NFS storage, you are required to create a separate and additional vmkernel portgroup to access your NFS storage. This way ESX Management traffic travels over one port group and NFS traffic travels over another.

In Xenserver the concept is similar; however executed much differently.

First and foremost you need to be aware of a few limitations in XenServer. While XenServer does allow you to create a dedicated nic (or bond) for NFS traffic, this nic must remain unmanaged by Xenserver. In contrast, a XenServer's management traffic travels over its "Management interface", which obviously has to be an interface that is managed via XenServer.

Allow me sum this up. You cannot share a nic or nics between management traffic and NFS traffic. This means that you are going want to create a bond for management traffic and a bond for NFS traffic you are going to need 4 free interfaces on your Xenserver box.

Now it is possible to use VLAN tagging and route your Management traffic and virtual machine traffic over the same physical interfaces. However its important to know that XenServer does not support VLAN tagging on the Management interface, so whatever VLAN you use for management, it must be the native vlan on the ports configuration.

The information below is from the Admin Guide for XenServer 5.5

Switch ports configured to perform 802.1Q VLAN tagging/untagging, commonly referred to as ports with a native VLAN or as access mode ports, can be used with XenServer management interfaces to place managementtraffic on a desired VLAN. In this case the XenServer host is unaware of any VLAN configuration.

XenServer management interfaces cannot be assigned to a XenServer VLAN via a trunk port.

Bottom line; its probably best to have seperate physical connections for your management traffic and NFS traffic.

Also, according to the Admin Guide, your NFS network should not be routed. See the words below and read them thusly.

"Before dedicating a network interface as a storage interface for use with iSCSI or NFS SRs, you must ensure that the dedicated interface uses a separate IP subnet which is not routable from the main management interface. If this is not enforced, then storage traffic may be directed via the main management interface after a host reboot, due to the order in which network interfaces are initialized."

Ok now that we got all that out of the way, lets actually create our dedicated storage nic.

First we need to get the uuid of the pif (physical interface) that we want to use. Note that this is just an example using a standalone interface.

#xe pif-list host-name-label=<"your_hostname>

Next we reconfigure our pif

#xe pif-reconfigure-ip mode=statc IP=<your-ip-on-nfs-vlan> netmask=<your-mask> uuid=<pif-uuid>

#xe pif-param-set disallow-unplug=true uuid=<pif-uuid>

#xe pif-param-set other-config:ManagementPurpose="Storage" uuid=<pif-uuid>

Alternatively you can use xe pif-forget to remote the interface from Xencenter database and configure it manually via the XenServer Kernel like you would any other interface in Linux, however this could be more confusing in the long run.