HP 3PAR StoreServ Cluster Extension Software Administrator Guide (5697-2894, December 2013)

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 storage system, it is
acknowledged to the local storage system. The write request is then acknowledged to the server.
User configuration file
HP 3PAR StoreServ Cluster Extension provides a user configuration file to customize failover
behavior. You can specify all customizable objects of HP 3PAR StoreServ Cluster Extension in this
file.
See “User configuration file” (page 54) for more information.
Force flag
The force flag forces HP 3PAR StoreServ Cluster Extension to skip the internal logic and enables
write access to the local virtual volumes regardless of the Remote Copy volume group member
state. You can set this flag when you are sure that the current site contains the latest data, even
though a previous application service startup process failed because HP 3PAR StoreServ Cluster
Extension discovered a Remote Copy volume group member state that could not be handled
automatically.
To use the force flag feature, before starting the application service that uses HP 3PAR StoreServ
Cluster Extension, you must create a file called application_name.forceflag in the directory
specified by the ApplicationDir property. While using clx3PARrun to use the force flag
feature, use the operand –forceflag to eliminate the need of creating the
application_name.forceflag file . The application_name.forceflag is the name of
the HP 3PAR StoreServ Cluster Extension resource. Before creating this file, ensure that the
application service is not running elsewhere. This file is removed after it is detected by HP 3PAR
StoreServ Cluster Extension.
You cannot use the force flag if the local virtual volume state is a combination of secondary and
syncing, which indicates that a copy operation is in progress. A disk cannot be put in read/write
access mode when a write operation is in progress to that virtual volume; in this case, HP 3PAR
StoreServ Cluster Extension returns a global error.
Planning for HP 3PAR StoreServ Cluster Extension
Consider the dependencies described in this section before configuring HP 3PAR StoreServ Cluster
Extension.
Cluster setup considerations
Windows clustering
Windows Clustering depends on a quorum resource to maintain a persistent log of cluster
configuration changes and status, as well as a single point to resolve any possible events that
could result in a split-brain situation. HP 3PAR StoreServ Cluster Extension supports the following
quorum configurations in which one site failure will not cause the entire cluster to fail.
Windows Server 2008/2008 R2/2012
• Node Majority
• Node and File Share Majority
NOTE: HP 3PAR StoreServ Cluster Extension does not support quorum configuration which
includes disk witness.
Planning for HP 3PAR StoreServ Cluster Extension 13