Sebastian Mogilowskis Blog

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Dell Equilogic iSCSI with XenServer 6.2

I using an Dell Equilogic PSM4110 Storage (Bladesystem) that only expose a single iSCSI target and one IQN, through one IP address. With default configurations of XenServer, it is not possible to establish multiple iSCSI connections with this kind of storage system. XenServer establishes only one connection per iSCSI target. The recommendation is to use NIC bonding to achieve failover and load balancing.

This is an alternative configuration for XenServer, whereby multiple iSCSI connections are established for a single iSCSI target. NIC bonding is not required.

1. Activate Multipath

First put your XenServer host into Maintenance Mode. (Right klick on the host in XenCenter and select “Enter Maintenance Mode”).

Right klick on server -> Properties -> Multipathing -> “Enable Multipathing on this server”.

You can change the iSCSI IQN of the host if you like, too.

2. Configurate iSCSI Interfaces

My iSCSI Interfaces are eth2 and eth3. Go to the “Networking” tab of your server and select “Properties” on both of your iSCSI Interfaces. Deactivate “Automatically add this network to new vitual machines” and change the MTU to 9000.

Now do the “IP Address Configuration” and two different IPs out of your iSCSI network IP range to your server. One for each interface.

storagenw1

storagenw2

Now move to your XenServer console and create iSCSI Interfaces:

iscsiadm -m iface --op new -I c_iface2
iscsiadm -m iface --op new -I c_iface3

and create Bridge Interfaces for this iSCSI Interfaces you had creaded:

iscsiadm -m iface --op update -I c_iface2 -n iface.net_ifacename -v xenbr2
iscsiadm -m iface --op update -I c_iface3 -n iface.net_ifacename -v xenbr3

3. Multipath Configuration

Next step is to change the multipath.conf

mv /etc/multipath.conf /etc/multipath.conf.bk
vi /etc/multipath.conf
devices {
  device {
    vendor "EQLOGIC" 
    product "100E-00" 
    path_grouping_policy multibus
    getuid_callout "/sbin/scsi_id -g -u -s /block/%n" 
    path_checker tur
    failback immediate
    path_selector "round-robin 0" 
    rr_min_io 3
    rr_weight priorities
  }
}

Reboot your server now and start connecting your iSCSI LUNs.

4. Test

You can test your configuration with this command:

multipath -ll

The output should look like this:

364ed2a058bc1baee78441503000040e4 dm-1 EQLOGIC,100E-00
size=100G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 11:0:0:0 sdc 8:32 active ready running
  `- 12:0:0:0 sdb 8:16 active ready running

5. Links

* http://support.citrix.com/article/CTX138429

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