Changing the cluster's cfmode setting

Reasons for changing the cfmode setting

Starting with version 7.1, Data ONTAP implements the use of the single_image mode for clustered systems. This cfmode setting provides the following advantages:

The host can access all LUNs through any target port on the cluster.
The single_image mode is supported on all storage systems.
The single_image mode is compatible with all supported FCP hosts and clustered storage systems that support the FCP protocol. There are no switch limitations. You can connect a storage system cluster in single_image mode to any FCP switch supported by Data ONTAP.

You might also want to change your cfmode setting to for the following reasons:

To increase the number of paths to the cluster-- For example, you might want to use the single_image setting to increase the number of available paths in your configuration. All ports on each storage system are available to access local LUNs. In addition, single_image node is available for all supported SAN hosts.
To support heterogeneous configurations--For example, you upgraded an existing SAN configuration with Solaris or Windows hosts and you want to add HP-UX or AIX hosts to the configuration.
HP-UX and AIX hosts do not support failover when the storage systems in a cluster are in standby mode. If you want to add these hosts to an existing homogenous configuration that has Solaris-only or Windows-only hosts, you have to change the cfmode setting on the storage system to either single_image or partner.

Solaris or Windows hosts in the same environment as HP-UX or AIX hosts must also have multipathing software installed when the cfmode setting is single_image or partner.

Impact of changing the cfmode setting

When you change the cfmode setting of the cluster to single_image, the following configuration components are affected.

Host access to LUNs
Hosts cannot access data on mapped LUNs. When you change the cfmode setting, you change the available paths between the host and the storage system cluster. Some previously available paths are no longer available and some new paths become available. The LUNs might be accessible but cannot be used until you reconfigure the host to discover the new paths. You must reconfigure every host that is connected to the cluster to discover the new paths. The LUNs are not accessible until you reconfigure the host. The procedure depends on your host operating system.
Multipathing software
If you have multipathing software in your configuration, changing the cfmode setting might also affect the multipathing policy.
Switch zoning
When you change the cluster's cfmode setting to single_image cfmode both nodes in the cluster use the same WWNN. One node assumes the WWNN of its partner. If your filer connects to a switch by using soft zoning (zoning by WWPN), you must update your zones to accommodate the WWNN change. Systems that connect to switches using hard (port) zoning are not affected.
Cabling
The single_image setting makes more target ports available to the host. This means you might have to change your cabling configuration.

Scheduling downtime

Changing the cfmode setting on the storage system requires host reconfiguration and in some cases you might have to reboot the host. The procedures also require you to quiesce host I/O and take host applications offline. It is recommended that you schedule downtime for your configuration before you change cfmode settings.

For detailed procedures

For procedures that describe how to change your cluster's cfmode setting to single_image mode, see the following documents:

FCP Host Compatibility Matrix at http://now.netapp.com/NOW/knowledge/docs/san/fcp_iscsi_config/
fcp_support.shtml.
The documentation for your Fibre Channel Host Attach Kit.