When using multipathed IBM XIV storage with native XenServer storage functionality (LVHD via FC or iSCSI), the multipath driver may not balance the load across all paths properly.

Background:

By default, XenServer’s multipath driver doesn’t have a specific configuration for an IBM XIV array, and rather uses a generic configuration. This configuration does not properly identify the characteristics of the paths/LUNs and therefore does not load balance the paths properly.

Notes:

  • The following configuration was employed on XenServer 6.0.2, but should be relevant with other versions of XenServer. The configuration resolved the issue and had positive effect, but was not rigorously tested.
  • This article does not go into detail on how to use the Linux command line to manipulate text files. Please refer to Linux documentation for further information.

Procedure:

The following should be completed on each XenServer host:

  • Evacuate VMs from the host, either by migration (Maintenance Mode) or shutdown
  • Connect to the CLI of the host, either through the console tab in XenCenter or through an SSH client (OpenSSH, Putty, etc.)
  • cd to /etc
  • Backup the multipath.conf file
  • Edit multipath.conf, adding the following “device” entry to the “devices” tree:
    multipath.conf
    device {
            vendor "IBM"
            product "2810XIV"
            selector "round-robin 0"
            path_grouping_policy multibus
            rr_min_io  32
            path_checker tur
            failback 15
            no_path_retry 5
            polling_interval 3
    }
  • Reboot the XenServer host