Designing Disaster Recovery Clusters using Metroclusters and Continentalclusters, Reprinted October 2011 (5900-1881)

1. Split the device group pair completely (pairsplit -g <dg> -S).
2. Re-create a pair from original PVOL as source (use the paircreate command).
3. Startup package on PVOL site (or SVOL site).
PVOL-PAIR with SVOL-PSUS(SSWS) State (for Continuous Access Journal Mode)
PVOL-PAIR with SVOL-PSUS(SSWS) is an intermediate state. The following is one scenario that
leads to this state:
• At T1, device pair is in PVOL-PAIR/SVOL-PAIR and the AP value is 0 in SVOL site.
• At T2, a failover occurs; package failover from PVOL site to SVOL site. The Metrocluster
Continuous Access issues SVOL-Takeover and the state will become SVOL-PSUS(SSWS) and
PVOL-PAIR.
• At T3, all Continuous Access links have been recovered. The state stays in SVOL-PSUS (SSWS)
and PVOL-PAIR. The duration the PVOL remains in PAIR state is relatively short
The PVOL-PAIR/SVOL-PSUS (SSWS) is an invalid state for P9000 or XP Asynchronous (both
Continuous Access/Asynchronous and Continuous Access Journal). In this state, by issuing a
pairresync or takeover command, it would fail. It is necessary to wait for the PVOL to become
PSUE.
Metrocluster with Continuous Access for P9000 and XP Device Group Monitor
In the Metrocluster/Continuous Access environment, where the device group state is not actively
monitored, it may not be apparent when the application data is not remotely protected for an
extended period of time. Under these circumstances, the P9000 or XP/Continuous Access device
group monitor provides the capability to monitor the status of the P9000 or XP/Continuous Access
device group used in a package. The P9000 or XP/Continuous Access device group monitor,
based on a pre-configured environment variable, also provides the ability to perform automatic
resynchronization of the P9000 or XP/Continuous Access device group upon link recovery.
NOTE: If the monitor is configured to automatically resynchronize the data from PVOL to SVOL
upon link recovery, a Business Copy (BC) volume of the SVOL should be configured as another
mirror.
In the case of a rolling disaster and the data in the SVOL becomes corrupt due to an incomplete
resynchronization, the data in the BC volume can be restored to the SVOL. This will result non-current,
but usable data in the BC volumes
The monitor, as a package service, periodically checks the status of the P9000 or XP/Continuous
Access device group that is configured for the package, and sends notification to the user via
email, syslog, and console if there is a change in the status of the package’s device group.
P9000 or XP/Continuous Access Device Group Monitor Operation Overview
The P9000 or XP/Continuous Access device group monitor runs as a package service. The user
can configure the monitor's setting through the package's environment file. Once the package has
started the P9000 or XP/Continuous Access device group monitor, the monitor will periodically
check the status of the P9000 or XP/Continuous Access device group. If there is a change in the
status or the monitor is configured to notify after an interval of no status change, the monitor will
send a notification that states the reason for the notification, a timestamp, and the status of the
P9000 or XP/Continuous Access device group.
Configuring the Monitor
Use the following steps to configure a monitor for a package’s device group:
• Configure the monitor’s variables in the package environment file.
• Configure the monitor as a service of the package.
Completing and Running a Metrocluster Solution with Continuous Access P9000 or XP 197