## 14.1 DR testing overview 

In a perfect world, DR testing is not needed. However, in reality, innumerable factors exist that can lead to a disaster that prevents the use of one or more of your production TS7700 clusters in a grid environment. Therefore, it is important to prepare and test your environment for such a scenario. 

The fortunate thing is that, in many cases, recovering from a disaster is easier and requires fewer steps than having to simulate a disaster and then clean up your disaster environment as though the simulation never occurred. Although general DR concepts are described in Chapter 5, “Disaster recovery” on page 201, this chapter focuses on concepts that are related to DR testing specifically. Examples are provided where needed and include step-by-step walkthroughs for the following methods that clients can use to accomplish DR testing in a TS7700 grid environment: 

GLYPH<SM590000> DR Testing by using FlashCopy 

GLYPH<SM590000> DR Testing by using Write Protect Mode on DR clusters 

GLYPH<SM590000> DR Testing without the use of Write Protect Mode on DR clusters 

GLYPH<SM590000> DR Testing by breaking the grid link connections to DR clusters 

All of these methods include advantages and disadvantages. It is important that before you decide which method to use, weigh these advantages and disadvantages against your environment and resources. Then, choose which method best fits your DR testing needs and ability. 

The description of each method assumes that you are familiar with the DR concepts that are presented in Chapter 5. The end of this chapter includes instructions for how to perform a DR test by using each method. Although it might be tempting to jump right to these instructions, it is recommended that you review this chapter in its entirety before DR testing to ensure that you are familiar with the concepts and options that are available for DR testing in a TS7700 grid environment. 

## 14.2 DR testing methods 

This section describes four methods that can be used to test disaster recovery in a TS7700 grid environment. Although the Copy Export function also can be used to test DR for a TS7700T (by using the copy exported tapes to rebuild a production environment on an empty TS7700T), this chapter focuses on DR testing that uses a grid environment that consists of production clusters and DR clusters. For more information about Copy Export, see Chapter 13, “Copy Export” on page 737. 

## 14.2.1 Method 1: DR Testing by using FlashCopy 

This method of DR testing uses the FlashCopy functionality that was introduced in Release 3.1. This function enables a DR host to perform testing against a point-in-time consistency snapshot while production operations and replication continue. With FlashCopy, production data continues to replicate during the entire DR test and the same virtual volume can be mounted at the same time by a DR host and a production host. 

