IBM DS8000 manual Global Mirror Asynchronous Pprc, Global Copy

Server write

1

2 Write acknowledge

Write to secondary (non-synchronously)

Figure 7-8 Global Copy

Global Mirror (Asynchronous PPRC)

Global Mirror provides a long-distance remote copy feature across two sites using asynchronous technology. This solution is based on the existing Global Copy and FlashCopy. With Global Mirror, the data that the host writes to the storage unit at the local site is asynchronously shadowed to the storage unit at the remote site. A consistent copy of the data is automatically maintained on the storage unit at the remote site.

Global Mirror operations provide the following benefits:

￿Support for virtually unlimited distances between the local and remote sites, with the distance typically limited only by the capabilities of the network and the channel extension technology. This unlimited distance enables you to choose your remote site location based on business needs and enables site separation to add protection from localized disasters.

￿A consistent and restartable copy of the data at the remote site, created with minimal impact to applications at the local site.

￿Data currency where, for many environments, the remote site lags behind the local site typically 3 to 5 seconds, minimizing the amount of data exposure in the event of an unplanned outage. The actual lag in data currency that you experience can depend upon a number of factors, including specific workload characteristics and bandwidth between the local and remote sites.

￿Dynamic selection of the desired recovery point objective, based upon business requirements and optimization of available bandwidth.

￿Session support whereby data consistency at the remote site is internally managed across up to eight storage units that are located across the local and remote sites.

Chapter 7. Copy Services 125