Performing Failover And Failback Operations (Without Global Mirror); Moving Production To Site B After Planned Outages (Failover) - IBM DS8000 User Manual

Performing failover and failback operations (without Global Mirror)

In the event of a planned outage, such as a scheduled maintenance or an
unplanned outage, such as a hardware failure that disables the operation of your
production site, you can perform a failover operation to your recovery site to
continue operations. After your production site is operational, you can perform a
subsequent failback operation to move production back to its original location.

Moving production to Site B after planned outages (failover)

When you schedule a planned outage at your production site (Site A), you can
switch production to your recovery site (Site B), allowing the processing of data to
resume at Site B. This process is known as a failover recovery.
The storage units at both Site A and Site B must be functional and accessible.
In a disaster recovery environment, when two storage units are set up in two
geographically distinct locations, the storage unit at the production or local site is
referred to as Site A and the storage unit at the remote or recovery site as Site B.
For this scenario, assume that all I/O to Site A has ceased because of a planned
outage, such as a scheduled maintenance. The failover operation is issued to the
storage unit that will become the primary. That is, production is moved to Site B
during this outage, which makes the target volumes at Site B convert to source
volumes and causes them to enter a suspended state. Your original source volumes
at Site A remain in the state they were in at the time of the site switch. Table 4 on
page 155 provides an example of the implementation of failover and failback
operations.
Note: The failover recovery operation does not reverse the direction of a remote
The following assumptions are made for this scenario:
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storage units) internally manages data consistency using consistency
groups within a Global Mirror configuration. Consistency groups can be
created many times per hour to increase the currency of data that is
captured in the consistency groups at the remote site.
Note: A consistency group is a collection of volumes (grouped in a
session) across multiple storage units that are managed together in a
session during the creation of consistent copies of data. The
formation of these consistency groups is coordinated by the master
storage unit, which sends commands over remote mirror and copy
links to its subordinate storage units.
In a two-site Global Mirror configuration, if you have a disaster at your
local site and have to start production at your remote site, you can use the
consistent point-in-time data from the consistency group at your remote
site to recover when the local site is operational.
In a three-site Metro/Global Mirror configuration, if you have a disaster at
your local site and you must start production at either your intermediate
or remote site, you can use the consistent point-in-time data from the
consistency group at your remote site to recover when the local site is
operational.
mirror and copy pair. It changes a target volume into a suspended source
volume, while leaving the source volume in its current state.