Mirror volumes were synchronous again, depended on the amount of data
being transferred. During this time, the Local B would be inconsistent if a
disaster were to have occurred.
Note: Previously, if you created a FlashCopy relationship with the
"Preserve Mirror, Required" option, using a Metro Mirror primary
volume as the target of that FlashCopy relationship, and if the status
of the Metro Mirror volume pair was not in a "full duplex" state, the
FlashCopy relationship failed. That restriction is now removed. The
Remote Pair FlashCopy relationship will complete successfully with
the "Preserve Mirror, Required" option, even if the status of the
Metro Mirror volume pair is either in a suspended or duplex
pending state.
Remote mirror and copy
The remote mirror and copy feature is a flexible data mirroring technology that
allows replication between a source volume and a target volume on one or two
disk storage units. You can also issue remote mirror and copy operations to a
group of source volumes on one logical subsystem (LSS) and a group of target
volumes on another LSS. (An LSS is a logical grouping of up to 256 logical
volumes for which the volumes must have the same disk format, either count key
data or fixed block.)
Remote mirror and copy is an optional feature that provides data backup and
disaster recovery. To use it, you must purchase at least one of the remote mirror
and copy 242x indicator feature and 239x function authorization features.
The remote mirror and copy feature provides synchronous (Metro Mirror) and
asynchronous (Global Copy) data mirroring. The main difference is that the Global
Copy feature can operate at very long distances, even continental distances, with
minimal impact on applications. Distance is limited only by the network and
channel extenders technology capabilities. The maximum supported distance for
Metro Mirror is 300 km.
Local Storage Server Remote Storage Server
Local A
Local B
Remote B
FlashCopy
f2c01089
Remote A
full duplex
Establish
FlashCopy
full duplex
Metro Mirror
Figure 14. Remote Pair FlashCopy
Chapter 3. Data management features 59
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