You have the option of implementing three different system configurations: a single-server configuration, a server-cluster configuration, and a cross-path configuration. The system configuration depends on the GAD solution that you are implementing.
The following table lists the GAD solutions and specifies the system configuration for each solution.
- GAD pairs both in the Mirrored status and in the Mirroring status are in the consistency group.
- GAD pairs both in the Mirrored status and in the Suspended status are in the consistency group.
When you use the cross-path configuration that enables both servers at the primary and secondary sites to access both volumes at the primary and secondary sites, the servers can continue to access the GAD volumes even in this situation. If you use a configuration other than the cross-path configuration, the servers cannot access the GAD volumes.
|
GAD solution |
Software |
System configuration |
|
|---|---|---|---|
|
Alternate path software |
Cluster software |
||
|
Continuous server I/O (if a failure occurs in a storage system) |
Required |
Not required |
Single-server configuration |
|
Failover and failback on the servers without using the storage systems |
Not required |
Required |
Server-cluster configuration |
|
Migration of a virtual machine of a server without using the storage systems |
Not required |
Required |
Server-cluster configuration |
|
Both of the following:
|
Required |
Required |
Cross-path configuration |
Single-server configuration
In a single-server configuration, the primary and secondary storage systems connect to the host server at the primary site. If a failure occurs in one storage system, you can use alternate path software to switch server I/O to the other site.
Server-cluster configuration
In a server-cluster configuration, servers are located at both the primary and secondary sites. The primary storage system connects to the primary-site server, and the secondary storage system connects to the secondary-site server. The cluster software is used for failover and failback. When I/O on the virtual machine of one server increases, you can migrate the virtual machine to the paired server to balance the load.
Cross-path configuration
In a cross-path configuration, primary-site and secondary-site servers are connected to both the primary and secondary storage systems. If a failure occurs in one storage system, alternate path software is used to switch server I/O to the paired site. The cluster software is used for failover and failback.
