Remote Array RAID Manager Instance

A remote array RAID Manager instance allows the Metrocluster package to determine the status of the device group on the remote P9000 or XP array even when the remote hosts are down or are inaccessible due to a network link failure. The remote array RAID Manager instance is configured on a node using the command device of the remote P9000 or XP array.

In a Metrocluster environment with Continuous Access P9000 or XP, the array at each site is interfaced only with the Metrocluster nodes in the same site using a command device in the array. When a Metrocluster package starts up on a node, the RAID Manager instance in the site communicates with the RAID Manager instance at the remote site to obtain the Continuous Access device group status. In situations where the remote hosts are down or are inaccessible due to a network link failure, the Continuous Access device group status cannot be determined. This occurs even when the remote array is up. Since data currency cannot be determined, the Metrocluster package startup fails for packages that have the AUTO_NONCURDATA parameter set to 0. Even if the package is started using FORCEFLAG, the P9000 or XP Continuous Access replication is suspended when the fence level is set to never.

Similarly, in a 2-node Metrocluster configuration that has a single node at each site, any node failure results in the other node not being able to determine the device group status. The subsequent failover of the Metrocluster packages to the surviving node may not succeed either.

In these situations, the remote array RAID manager instance allows the Metrocluster package to determine the device group status and start successfully. The remote array RAID Manager requires access to a command device configured on the remote array. Access to this command device at the remote array can be configured using one of the following methods:

•Using the P9000 or XP external storage feature (Remote Command Device)

A Remote Command Device (RCMD) is a device to which a command device in a remote XP array is mapped. The RCMD is configured using the P9000 or XP external storage feature, through inter-site replication links. On P9000 or XP array in a Metrocluster site, a command device from the P9000 or XP array at the remote site is mapped to the local device using the P9000 or XP external storage feature. The mapped command device is then presented to the nodes in the site to be used as a remote command device. This RCMD configuration is done between arrays on both sites in a mutual fashion. For more information on the behavior of the command device of a remote P9000 or XP array, see the HP StorageWorks P9000 External Storage for Open and Mainframe Systems User Guide or HP StorageWorks XP External Storage user guide available at the following location:

http://bizsupport1.austin.hp.com/bizsupport/TechSupport/ProdSearch.jsp? prod=HP%20StorageWorks—> HP StorageWorks XP Array Manager Software —> Manuals.

•Using extended SAN

The dedicated command device from the P9000 or XP array in the remote site is directly presented to the nodes in the local site over an extended SAN. This configuration does not use the XP external storage feature.

HP recommends configuring a remote array RAID Manager instance in all Metrocluster configurations, especially in a 2-node configuration, as it is more robust. For more information on configuring a remote array RAID Manager instance in Metrocluster, see “Configuring a remote array RAID Manager instance” (page 170).

NOTE:

•Remote command device can be configured in Continentalclusters.

•Remote command device need not be configured when P9000 or XP Continuous Access Journal replication is used.

158 Building Disaster Recovery Serviceguard Solutions Using Metrocluster with Continuous Access for P9000 and XP