HyperSwap function

The IBM® HyperSwap® function is a high availability feature that provides dual-site access to a volume. HyperSwap functions are available on systems that can support more than one I/O group.

When you configure a system with a HyperSwap topology, the system configuration is split between two sites for data recovery, migration, or high availability use cases. When a HyperSwap topology is configured, each node or enclosure, external storage system, and host in the system configuration must be assigned to one of the sites in the topology. Both of an I/O group must be at the same site. This site must be the same site of the external storage systems that provide the managed disks to that I/O group. When managed disks are added to storage pools, their site attributes must match. This requirement ensures that each copy in a HyperSwap volume is fully independent and is at a distinct site.

When the system is configured between two sites, HyperSwap volumes have a copy at one site and a copy at another site. Data that is written to the volume is automatically sent to both copies. If one site is no longer available, the other site can provide access to the volume. If you are using ownership groups to manage, access to HyperSwap volumes, both volume copies and users who access them must be assigned to the same ownership group.

A 2-site HyperSwap configuration can be extended to a third site for disaster recovery that uses the IBM Spectrum Virtualize 3-Site Orchestrator. IBM Spectrum Virtualize 3-Site Orchestrator coordinates replication of data for disaster recovery and high availability scenarios between systems that are on three geographically dispersed sites. IBM Spectrum Virtualize 3-Site Orchestrator is a command-line based application that runs on a separate Linux host and configures and manages supported replication configurations on IBM Spectrum Virtualize products. To extend an existing HyperSwap system or to create a new HyperSwap configuration with IBM Spectrum Virtualize 3-Site Orchestrator requires additional planning, installing, and configuring steps.

When you create HyperSwap volumes, a HyperSwap relationship is created automatically between the copies at each site. These relationships automatically run and switch direction according to which copy or copies are online and up to date. The relationships provide access to whichever copy is up to date through a single volume, which has unique ID. Relationships can be grouped into consistency groups just like other types of remote-copy relationships. The consistency groups fail over consistently as a group based on the state of all copies in the group. An image that can be used for disaster recovery is maintained at each site.

The Small Computer System Interface (SCSI) protocol allows storage devices to indicate the preferred ports for hosts to use when they submit I/O requests. Using the Asymmetric Logical Unit Access (ALUA) state for a volume, a storage controller can inform the host of which paths are active and which ones are preferred. In a HyperSwap system topology, the system suggests that the host use local nodes over remote nodes. A local is a node that is configured at the same site as the host.