HP StorageWorks EVA Cluster Extension Software Administrator Guide (T3667-96045, April 2010)

One-to-one configuration
When setting up a one-to-one configuration (see Figure 2 on page 18), consider the following:
• Cluster host nodes are split between two or more geographically dispersed data center sites and
use redundant, diversely routed network connections for intra-cluster communications. Those links
must be as reliable as possible to prevent false failover operations or split-brain situations.
• Each cluster host node connected to an EVA storage system should have redundant I/O paths to
the EVA storage system. Connections to both the source (primary) and the destination (secondary)
copy of the application disk set are not allowed from the same host. Configure your servers only
in the zone that allows access to the local EVA storage system.
• HP recommends a minimum of two cluster host nodes per site. This allows for preferred local failover
in case of system failure. Local failover operations are faster than remote failover between EVA
storage systems because you do not need to change the mirroring direction of the DR group
members.
• You can deploy EVA Cluster Extension in environments where several clusters use the same EVA
storage system pair.
• You can use Continuous Access EVA in synchronous replication mode with Continuous Access
EVA between two EVA storage systems connected using FC switches and extender hardware.
• You can use Continuous Access EVA in enhanced asynchronous mode with EVA Cluster Extension
4.00.00 and later for Windows.
NOTE:
For complete information on which write modes are supported on each version of controller
software, see the HP StorageWorks Enterprise Virtual Array Compatibility Reference .
• EVA Cluster Extension supports Continuous Access EVA in synchronous replication mode and en-
hanced asynchronous replication mode in the following configurations:
• Switched FC connection (dual-fabric intersite links)
• FC to DWDM networks, via FC switches
• FC over IP networks, via FC switches as shown in the HP StorageWorks Continuous Access
EVA Implementation Guide
• The Continuous Access EVA links must have redundant, separately routed links for each fabric.
The cluster network must have redundant, separately routed links. However, cluster networks and
Continuous Access EVA can share the same links if the link technology is protocol independent
(for example, WDM) or if the FC protocol is transformed into IP.
EVA Cluster Extension Software Administrator Guide 17