## Requirement: No physical tape or dark site 

Some clients want to eliminate physical tape from one or more data center locations. The TS7760C, TS7700D, or a hybrid configuration supports these requirements. The complete elimination of physical tape might not be the ideal configuration; therefore, TS7700T clusters can exist at alternative locations. 

## Requirement: Big data 

The TS7700T is attached to an IBM TS3500 or IBM TS4500 tape library and can store multiple PB of data while still supporting writes at disk speeds and read hit ratios up to 90% for many workloads. Depending on the size of your tape library (the number of library frames and the capacity of the tape cartridges that are being used), you can store up to 100 PB of compressed data. 

## Requirement: Offsite vault of data for DR purposes with Copy Export 

Some clients require an extra copy on physical tape, require a physical tape to be stored in a vault, or depend on the export of physical tape for their DR needs. For these accounts, the TS7700T is ideal. 

## Requirement: Workload movement with Copy Export 

In specific use cases, the data that is associated with one or more workloads must be moved from one grid configuration to another without the use of TCP/IP. Physical tape and TS7700T Copy Export with merge (available as a service offering) provide this capability. 

## 2.5.2 Planning for high availability or DR in limited distances 

In many HA configurations, two TS7700 clusters are located within  metro distance of each other. They are in one of the following situations: 

GLYPH<SM590000> The same data center within the same room 

GLYPH<SM590000> The same data center, in different rooms 

GLYPH<SM590000> Separated data centers, on a campus 

GLYPH<SM590000> Separated data centers, at a distance in the same metropolitan area 

These clusters are connected through a local area network (LAN). If one of them becomes unavailable because it failed, is being serviced, or is being updated, data can be accessed through the alternative TS7700 Cluster until the unavailable cluster is available. The assumption is that continued access to data is critical and no single point of failure, repair, or upgrade can affect the availability of data. 

For these configurations, the multi-cluster grid can act as an HA and DR configuration that assumes that all host and disk operations can recover at the metro distant location. However, metro distances might not be ideal for DR because some disasters can affect an entire metro region. In this situation, a third location is ideal. 

## Configuring for high availability or metro distance 

As part of planning a TS7700 Grid configuration to implement this solution, consider the following points: 

GLYPH<SM590000> Plan for the virtual device addresses in both clusters to be configured to the local hosts. 

GLYPH<SM590000> Plan a redundant FICON attachment of both sites; that is, an extender that is longer than 10 km (6.2 miles) for the FICON connections is suggested. 

