Remote Mirror And Copy - IBM TotalStorage DS6000 Introduction And Planning Manual

Note: If you perform a resync operation, it is sent to any source and volume pair.

Remote Mirror and Copy

Remote mirror and copy is a storage server feature that constantly updates a target
copy of a volume so that it matches changes that were made to its associated
source volume.
The remote mirror and copy feature is a hardware solution that enables the
mirroring of data from one site (the local site) and its associated volumes (source
volumes) to a second storage unit at another site (the recovery or remote site) and
its volumes (target volumes).
Note: Remote mirror and copy was referred to as Peer-to-Peer Remote Copy
Remote mirror and copy differs from FlashCopy in two essential ways. First, the
source and target volumes can be on the same storage server or on separate
storage servers that are located at some distance from each other. Second, and
more significantly, remote mirror and copy does not capture the state of the source
volume at some point in time, but rather reflects all changes that were made on the
source volume to the target volume.
The following modes of operation are available:
IBM TotalStorage Global Copy
IBM TotalStorage Global Mirror
IBM TotalStorage Metro Mirror
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Introduction and Planning Guide
All source and target volume pairs will be re-synchronized, not just the one
pair that you selected.
(PPRC) in earlier documentation for the IBM TotalStorage Enterprise Storage
Server. Currently, the remote mirror and copy feature name is used
generically for all methods of synchronous and asynchronous methods. In
addition, in a remote mirror and copy environment, a site where production
applications run might be referred to as the production site, local site, or Site
A. A site that has mirrored data of your local site might be referred to as a
recovery site, backup site, remote site, or Site B.
Global Copy copies data nonsynchronously and over longer distance than
is possible with Metro Mirror. In Global Copy mode, the source volume
sends a periodic, incremental copy of updated tracks to the target volume
instead of a constant stream of updates. Because the original order of
updates is not strictly maintained, this is considered a "fuzzy" copy. All
updates that an attached host performs on the source volume are also
performed on the target volume, but at a later time.
Global Mirror copying provides a two-site extended distance remote copy
option for disaster recovery. This solution is based on 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 then automatically
maintained on the storage unit at the remote site.
Metro Mirror synchronously mirrors updates that are done to source
volumes. All updates that any attached host performs on the source volume
are also performed on the target volume before operation completion is
indicated. Metro Mirror copying supports a maximum distance of 300 km
(186 mi).