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

HP Continuous Access EVA
Figure 4 on page 20 shows the supported EVA Cluster Extension configuration.
Figure 4 Supported EVA Cluster Extension storage system configuration
.
Synchronous replication
Using synchronous mode, all write requests from the server are first transferred to the remote storage
system. After each I/O has been mirrored in the cache area of the remote array, it is acknowledged
to the local storage system. The write request is then acknowledged to the server.
Asynchronous replication (Windows only)
Enhanced asynchronous mode is supported by EVA Cluster Extension for Windows 4.00.00 and
later.
Using asynchronous mode, the source array acknowledges I/O completion before replicating the
data on the destination array. Asynchronous replication prioritizes response time over data currency.
Enhanced asynchronous write mode uses the write history log for the DR group as a journal to hold
I/Os waiting to be replicated to the remote array.
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 .
HP Continuous Access EVA DR groups
You must configure a single DR group for a cluster group in MSCS. This DR group must include all
vdisks being used for the application service.
The DR group is the unit in which EVA Cluster Extension failover operations are carried out.
EVA Cluster Extension features20