Configuring The System For Multipathing; Preparing San Devices For Multipathing; Section 5.4, "Configuring The System For Multipathing - Novell LINUX ENTERPRISE SERVER 10 - STORAGE ADMINISTRATION GUIDE 7-2007 Administration Manual

The multipath -t command shows an internal table of storage subsystems that require special
handling. It is not an exhaustive list of supported storage subsystems. It lists only those arrays that
require special handling and that the multipath-tools developers had access to during the tool
development. Arrays with true active/active multipath support do not require special handling, so
they are not listed here. A listing in the table does not necessarily mean that SUSE Linux Enterprise
Server was tested on that specific hardware.
Some hardware might require manual configuration in the /etc/multipath.conf file in order
for multipathing to work. For information about manual configuration, see
Support for the Storage Subsystem to /etc/multipath.conf," on page
Storage subsystems that require special commands on failover from one path to the other or that
require special nonstandard error handling might require more extensive support. Therefore, the
Device Mapper tool has hooks for hardware handlers. For example, one such handler for the EMC
CLARiiON CX family of arrays is already provided. Consult the hardware vendor's documentation
to determine if its hardware handler must be installed for Device Mapper.

5.4 Configuring the System for Multipathing

Section 5.4.1, "Preparing SAN Devices for Multipathing," on page 47
Section 5.4.2, "Partitioning Multipathed Devices," on page 48
Section 5.4.3, "Configuring the Server for Multipathing," on page 48
Section 5.4.4, "Configuring mdadm.conf and lvm.conf to Scan Devices by UUID," on page 48

5.4.1 Preparing SAN Devices for Multipathing

Before configuring multipath I/O for your SAN devices, prepare the SAN devices, as necessary, by
doing the following:
Configure and zone the SAN with the vendor's tools.
Configure permissions for host LUNs on the storage arrays with the vendor's tools.
Install the Linux HBA driver module. Upon module installation, the driver automatically scans
the HBA to discover any SAN devices that have permissions for the host. It presents them to
the host for further configuration.
NOTE: Ensure that the HBA driver you are using does not have native multipathing enabled.
See the vendor's specific instructions for more details.
After the driver module is loaded, discover the device nodes assigned to specific array LUNs or
partitions.
If the LUNs are not seen by the HBA driver, lsscsi can be used to check whether the SCSI
devices are seen correctly by the operating system. When the LUNs are not seen by the HBA driver,
check the zoning setup of the SAN. In particular, check whether LUN masking is active and whether
the LUNs are correctly assigned to the server.
If the LUNs are seen by the HBA driver, but there are no corresponding block devices, additional
kernel parameters are needed to change the SCSI device scanning behavior, such as to indicate that
LUNs are not numbered consecutively. For information, see
(http://www.novell.com/support/search.do?cmd=displayKC&docType=kc&externalId=http--
Section 5.7, "Adding
50.
Options for SCSI Device Scanning
Managing Multipath I/O for Devices 47