A typical global-active device system consists of storage systems, paired volumes, a consistency group, a quorum disk, a virtual storage machine, paths and ports, alternate path software, and cluster software.
The following illustration shows the components of a typical global-active device system.
Storage systems
Both of the primary and secondary storage systems should be the same model type, but they do not have to be the same model. For example:- If the primary storage system is a VSP 5000 series, the secondary storage system must also be a VSP 5000 series, VSP E series, or VSP G/F350, G/F370, G/F700, G/F900.
- If the primary storage system is a VSP G1x00 or a VSP F1500, the secondary storage system can be a VSP E series, or VSP G/F350, G/F370, G/F700, G/F900.
- If the primary storage system is a VSP G350, G370, G700, G900, the secondary storage system can be a VSP G350, G370, G700, G900.
- If the primary storage system is a VSP F350, F370, F700, F900 storage system, the secondary storage system can be VSP F350, F370, F700, F900.
- If the primary storage system is a VSP G1000, the secondary storage system must also be a VSP G1000.
An external storage system or iSCSI-attached server that is connected to the primary and secondary storage systems using Universal Volume Manager is required for the quorum disk.
Paired volumes
A global-active device pair consists of a P-VOL in the primary storage system and an S-VOL in the secondary storage system. For model connectivity support requirements, refer to System requirements.
Consistency group
A consistency group consists of multiple global-active device pairs. By registering GAD pairs to a consistency group, you can resynchronize or suspend the GAD pairs by consistency group.
For details about storage system support (microcode) for consistency groups, refer to Requirements and restrictions.
Quorum disk
The quorum disk, required for global-active device, determines the storage system on which server I/O should continue when a storage system or path failure occurs. The quorum disk is virtualized from an external storage system that is connected to both the primary and secondary storage systems. Alternatively, a disk in an iSCSI-attached server can be used as a quorum disk if the server is supported by external storage. If you do not set a volume for the quorum disk, you do not need to prepare a volume in an external storage system for the quorum disk.
Virtual storage machine
A virtual storage machine (VSM) is configured in the secondary storage system with the same model and serial number as the (actual) primary storage system. The servers treat the virtual storage machine and the storage system at the primary site as one virtual storage machine.
You can create GAD pairs using volumes in virtual storage machines. When you want to create a GAD pair using volumes in VSMs, the VSM for the volume in the secondary site must have the same model and serial number as the VSM for the volume in the primary site.
Paths and ports
GAD operations are carried out between hosts and primary and secondary storage systems that are connected by data paths composed of one of more physical links.
The data path, also referred to as the remote connection, connects ports on the primary storage system to ports on the secondary storage system. Both Fibre Channel and iSCSI remote copy connections are supported. The ports have attributes that enable them to send and receive data. One data path connection is required, but you should use two or more independent connections for hardware redundancy.
Alternate path software
Alternate path software is used to set redundant paths from servers to volumes and to distribute host workload evenly across the data paths. Alternate path software is required for the single-server and cross-path GAD system configurations.
Cluster software
Cluster software is used to configure a system with multiple servers and to switch operations to another server when a server failure occurs. Cluster software is required when two servers are in a global-active device server-cluster system configuration.