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Chapter 6. Copy Services 99
Figure 6-8 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 server enclosure at the local site is
asynchronously shadowed to the server enclosure at the remote site. A consistent copy of the
data is then automatically maintained on the server enclosure 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.
2
1
Server write
Write to secondary
(non-synchronously)
Write acknowledge