D Single Path Implementation
This appendix provides guidance for connecting servers with a single path host bus adapter (HBA)
to the Enterprise Virtual Array (EVA) storage system with no multi-path software installed. A single
path HBA is defined as an HBA that has a single path to its LUNs. These LUNs are not shared by any
other HBA in the server or in the SAN.
The failure scenarios demonstrate behavior when recommended configurations are employed, as well
as expected failover behavior if guidelines are not met. To implement single adapter servers into a
multi-path EVA environment, configurations should follow these recommendations.
NOTE:
The purpose of single HBA configurations for non-mission critical storage access is to control costs.
This appendix describes the configurations, limitations, and failover characteristics of single HBA
servers under different operating systems. Much of the description herein are based upon a single
HBA configuration resulting in a single path to the device, but such is not the case with OpenVMS
and Tru64 UNIX.
HP OpenVMS and Tru64 UNIX have native multi-path features by default.
With OpenVMS and Tru64 UNIX, a single HBA configuration will result in two paths to the device
by virtue of having connections to both EVA controllers. Single HBA configurations are not single
path configurations with these operating systems.
In addition, cluster configurations of both OpenVMS and Tru64 UNIX provide enhanced availability
and security. To achieve availability within cluster configurations, each member should be configured
with its own HBA(s) and connectivity to shared LUNs. Cluster configuration will not be discussed
further within this appendix as the enhanced availability requires both additional server hardware
and HBAs which is contrary to controlling configuration costs for non-mission critical applications.
For further information on cluster configurations and attributes, see the appropriate operating system
guides and the SAN design guide.
NOTE:
HP continually makes additions to its storage solution product line. For more information about the
HP Fibre Channel product line, the latest drivers, and technical tips, and to view other documentation,
see the HP website at
http://www.hp.com/country/us/eng/prodserv/storage.html
High-level solution overview
EVA was designed for highly dynamic enterprise environments requiring high data availability, fault
tolerance, and high performance; thus, the EVA controller runs only in multi-path failover mode.
Multi-path failover mode ensures the proper level of fault tolerance for the enterprise with mission-critical
application environments. However, this appendix addresses the need for non-mission-critical
applications to gain access to the EVA system running mission-critical production applications.
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