HP 3PAR Operating System Software - Manual (Page 19)

Figure 6 Synchronous Long Distance Remote Copy - One Backup System Failure
In this example, when System2 is restored, Remote Copy transfers data from System1 to System2
and restores synchronous mode Remote Copy between System1 and System2.
If the Primary System Fails
If the primary system in a Synchronous Long Distance Remote Copy configuration fails, one of the
backup systems (typically the backup system that shares a synchronous connection with the primary
system) assumes the role of the primary system, and the second backup system serves as the backup
system to the temporary primary system. The volume on the temporary primary system is updated
periodically on the backup system.
Figure 7 (page 20) illustrates a Synchronous Long Distance configuration in which primary system
System1 goes down. In this example, System2 becomes the temporary primary system, and System3
becomes the backup system to System2.
NOTE: You can set up either backup system to assume the role of the primary system in the event
of failover.
Synchronous Long Distance Configuration 19