What Is Mirrorview/A - EMC CX700 Planning Manual

Data Replication and Data Mobility Software

What Is MirrorView/A?

MirrorView/A is storage-system-based software for periodically
updating remote copies of production data. It keeps a point-in-time
copy of a logical unit (LUN) and periodically replicates the copy to a
separate location to provide disaster recovery; that is, to let one image
continue to be active if a serious accident or natural disaster disables
the other. It provides data replication over long distances (hundreds
to thousands of miles).
The production image (the one mirrored) is called the primary image;
the copy image is called the secondary image. MirrorView/A
supports one remote image per primary. The primary image receives
I/O from a host called the production host; a separate storage system
maintains the secondary image. This storage system can optionally
have a failover/standby server connected to it or can be connected to
its own server. Both storage systems are managed with the same
domain. The management station can promote the secondary image
if the primary image becomes inaccessible. After initial
synchronization, the remote site always has a consistent copy of the
primary data.
Like all remote mirroring products, MirrorView/A does not flush host
buffers before replicating the primary data. Therefore, the copy is a
crash-consistent image of the primary data. You must verify data integrity of
the secondary image before using it for disaster recovery. (The verification
process varies by application type.)
MirrorView/A supports MirrorView/A Consistency Groups, which
this manual refers to as Consistency Groups. A Consistency Group is a
collection of asynchronous mirrors that must remain intact during
any disruptive situations. When you mirror different LUNs
asynchronously that contain data with a content relationship to each
other (such RDBMS database files and transaction logs), the
mirroring software must update the secondary images of these LUNs
in a way that retains their point-in-time content relationship to each
other. If this relationship is not retained, the application may not be
able to use the data in the secondary image LUNs should a failure
occur with a primary image LUN.
The LUNs in a MirrorView/A Consistency Group must reside on the same
storage system, unlike the volumes in a Symmetrix Consistency Group,
which can reside on multiple storage systems.
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What Is MirrorView/A?