When creating disk groups and distributing Vdisks within them, sufficient capacity must remain for log disks to expand to their maximum level. The log is declared full, and reaches its maximum level, whenever the first of the following conditions is reached:

•The size of the log data file exceeds twice the capacity of the DR group.

•No free space remains in the physical disk group.

•The log reaches 2 TB of Vraid1 (4 TB total).

Copy Sets

Vdisks are user-defined storage allotments of virtual or logical data storage. A pairing relationship can be created to automatically replicate a logical disk to another logical disk. The generic term for this is a copy set. A relationship refers to the arrangement created when two storage systems are partnered for the purpose of replicating data between them. A Vdisk does not have to be part of a copy set. Vdisks at any site can be set up for local storage and used for activities such as testing and backup. Clones and snapclones are examples of Vdisks used in this manner. When a Vdisk is not part of a copy set, it is not disaster tolerant, but it can use various Vraid types for failure tolerance.

Managed Sets

A managed set is a collection of DR groups selected for the purpose of managing them. For example, a managed set can be created to manage all DR groups of a particular application that reside in separate storage arrays.

Failover

The recovery process whereby one DR group, managed set, fabric, or controller switches over to its backup is called a failover. The process can be planned or unplanned. A planned failover allows an orderly shutdown of the system before the redundant system takes over. An unplanned failover occurs when a failure or outage occurs that may not allow an orderly transition of roles. Listed below are several types of Continuous Access EVA failovers:

•DR group failover: An operation to reverse the replication direction of a DR group. A DR group can have a relationship with only one other DR group, and a storage system can have a relationship with only one other storage system.

•Managed set failover: An operation to reverse the replication direction of all DR groups in the managed set.

•Fabric or path failover: The act of transferring I/O operations from one fabric or path to another.

•Controller failover: When a controller assumes the workload of its partner (within the same storage system).

Continuous Access EVA Management Software

Metrocluster Continuous Access EVA requires the following two software components to be installed in the Management Server:

•HP StorageWorks Command View EVA (CV EVA). This software component allows you to configure and manage the storage and DR group via a web browser interface.

•Storage Management Interface Specification (SMI-S). The SMI-S EVA software provides the Storage Management Interface Specification (SMI-S) interface for the management of EVA arrays. Metrocluster Continuous Access EVA software uses WBEM API to communicate with SMI-S to automatically manage the DR Groups that are used in the application packages.

Overview of EVA and Continuous Access EVA Concepts 215