HP 4000.6000.8000 Enterprise Virtual Arrays - Manual (Page 145)

E 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.
The non-mission-critical applications gain access to the EVA from a single path HBA server without
running a multi-path driver. When a single path HBA server uses the supported configurations, a
fault in the single path HBA server does not result in a fault in the other servers.
Benefits at a glance
The EVA is a high-performance array controller utilizing the benefits of virtualization. Virtualization
within the storage system is ideal for environments needing high performance, high data availability,
fault tolerance, efficient storage management, data replication, and cluster support. However,
enterprise-level data centers incorporate non-mission-critical applications as well as applications
that require high availability.
Single-path capability adds flexibility to budget allocation. There is a per-path savings as the
additional cost of HBAs and multi-path software is removed from non-mission−critical application
requirements. These servers can still gain access to the EVA by using single path HBAs without
multi-path software. This reduces the costs at the server and infrastructure level.
High-level solution overview 145