Citrix Systems 6 Storage Multipathing

†Storage pool probing is only possible at sr-create time. It needs to be done there so that the aggregate can be specified at the point that the

SR is created.

‡If the username, password, or port configuration of the StorageLink service are changed from the default value then the appropriate parameter

and value must be specified.

Storage Multipathing

Dynamic multipathing support is available for Fibre Channel and iSCSI storage backends. By default, it uses round-

robin mode load balancing, so both routes have active traffic on them during normal operation. You can enable

multipathing in XenCenter or on the xe CLI.

Before attempting to enable multipathing, verify that multiple targets are available on your

storage server. For example, an iSCSI storage backend queried for sendtargets on a given

portal should return multiple targets, as in the following example:

iscsiadm -m discovery --type sendtargets --portal 192.168.0.161

192.168.0.161:3260,1 iqn.strawberry:litchie

192.168.0.204:3260,2 iqn.strawberry:litchie

1. Unplug all PBDs on the host:

xe pbd-unplug uuid=<pbd_uuid>

2. Set the host's other-config:multipathing parameter:

xe host-param-set other-config:multipathing=true uuid=host_uuid

3. Set the host's other-config:multipathhandle parameter to dmp:

xe host-param-set other-config:multipathhandle=dmp uuid=host_uuid

4. If there are existing SRs on the host running in single path mode but that have multiple paths:

• Migrate or suspend any running guests with virtual disks in affected the SRs

• Unplug and re-plug the PBD of any affected SRs to reconnect them using multipathing:

xe pbd-plug uuid=<pbd_uuid>

To disable multipathing, first unplug your VBDs, set the host other-config:multipathing

parameter to false and then replug your PBDs as described above. Do not modify the other-

config:multipathhandle parameter as this will be done automatically.

Multipath support in XenServer is based on the device-mapper multipathd components. Activation and

deactivation of multipath nodes is handled automatically by the Storage Manager API. Unlike the standard dm-

multipath tools in Linux, device mapper nodes are not automatically created for all LUNs on the system, and

it is only when LUNs are actively used by the storage management layer that new device mapper nodes are

provisioned. Therefore, it is unnecessary to use any of the dm-multipath CLI tools to query or refresh DM

table nodes in XenServer. Should it be necessary to query the status of device-mapper tables manually, or list

active device mapper multipath nodes on the system, use the mpathutil utility:

• mpathutil list

• mpathutil status

Note:

Due to incompatibilities with the integrated multipath management architecture, the

standard dm-multipath CLI utility should not be used with XenServer. Please use the

mpathutil CLI tool for querying the status of nodes on the host.

Note: