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Planning ESS Copy Services configuration
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See "Planning ESS Copy Services configuration" for examples of site configurations
for PPRC.
This section provides examples of site configurations for Copy Services, and
explains why you might select a particular configuration.
Example of a PPRC operational environment
For this example, assume that you have two sites, Site A and Site B. Each Site has
a set of ESSs connected to the network. One of the ESS clusters at Site A has
been configured as the ESS Web Copy Services primary server. One of the clusters
at Site B has been configured as the ESS Web Copy Services backup server. Host
systems at both Site A and Site B have installed the CLI for control of ESS Copy
Services. ESS Copy Services code keeps data synchronized between the primary
and the backup server.
If for some reason, the Copy Services primary server is down, you can change the
management of all the ESS clusters to the backup Copy Services server. The
secondary Copy Services server then takes over the management of all the
remaining ESSs.
A typical PPRC physical configuration might include:
v A single logical storage server that is shadowed to a single secondary logical
subsystem
v All devices or a subset of devices in PPRC pairs
This applies to a user who might have:
v All production applications and data located in a primary site
v All secondary data located at a disaster-recovery site
Shadowing all data that is associated with a server to a backup site reduces the
operational management complexity. This includes determining what data (on a
file-by-file basis) the backup site requires to recover the application in the event of a
disaster since all data is replicated at the secondary site.
A single storage server mirrored to a secondary server
IBM recommends mirroring all logical subsystems at the primary site to an identical
logical subsystem at the secondary site. This includes:
v All production applications and data located in a primary site
v All secondary data located in a secondary or disaster recovery site. For more
information on disaster recovery, see the IBM Enterprise Storage Server Web
Interface User's Guide .
Generally, the files associated with an application or application set are dynamic in
many environments. Consequently, you may choose to mirror all of the application
data. This configuration requires minimal application storage-management analysis
to guarantee optimal performance.
Bi-directional mirroring
With bi-directional mirroring, half of the devices are mirrored from ESS A to ESS B.
The remaining half are mirrored from ESS B to ESS A.
This configuration distributes all inputs/outputs (I/O) across two ESSs instead of
directing them to a single primary ESS.
Chapter 2. Planning the physical configuration
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