TS7700 system components

Nodes, Clusters, and Grid

The TS7700 is built on a distributed node architecture. The nodes perform either virtualization (vNode) or hierarchical data storage management (hNode). The vNode presents the virtual image of a library(ies) and the drives to a host system. When the TS7700 is attached to a physical library, the vNode also receives tape drive and library requests from the host and processes them as real devices do. It then translates the tape requests through a virtual drive and uses a file in a file system to represent the virtual tape image. Once created or altered by the host system through a vNode, a virtual volume resides in disk cache or on physical tape, where it is managed by the hNode. When the TS7700 is attached to a physical library, the hNode is the only node that is aware of physical tape resources and the relationships between the virtual and physical volumes. The hNode is also responsible for any replication of the virtual volumes and their attributes across site boundaries.

Based on the node architecture, a vNode or hNode can run on separate virtualization hardware or be combined to run on the same hardware. When a vNode and hNode are combined to run on the same virtualization hardware, they are referred to collectively as a General Node, or gNode. The TS7700 runs a gNode. See Figure 1 for an illustration of the relationship between nodes.

The TS7700 Cluster combines the TS7700 Server with a disk subsystem, the TS7700 Cache Controller. This architecture permits additional disks or nodes to be added in future offerings to expand the capabilities of the system. Figure 2 displays a TS7700 configured as a cluster.

The TS7700 Grid, or grid configuration, is a series of two or more clusters that are connected to one another to form a high availability or disaster recovery solution. Virtual volume attributes and data are replicated across the clusters in a grid to ensure the continuation of production work, should a single cluster become unavailable.

A virtual volume can be accessed from any virtual device in the system, even if the virtual volume has only a single replica. Should a failure occur at the source cluster, replicated virtual volumes are still available since any data that is replicated between the clusters is accessible through any other cluster in a grid configuration. Each copy is a valid source of the virtual volume. A grid configuration looks like a single storage subsystem to the hosts attached to the clusters; it can be described as a composite library with underlying distributed libraries similar to the prior generation's peer-to-peer (PTP) VTS. For more information about data accessibility in the event of a source cluster failure, see The Autonomic Ownership Takeover Manager.

A TS7700 Grid can be created by using TS7700 disk-only clusters, TS7700 tape-attached clusters, or a combination of both.

Multiple TS7700 Grids can be attached to the same host system yet operate independent of one another.

†FICON channel extenders are optional.

Operational components

The configuration of these components differs depending on whether a TS7700 is configured as a TS7760, TS7720, or a TS7740.