Chapter 10. Disaster Recovery Using Copy Services - IBM DS8000 User Manual

Chapter 10. Disaster recovery using Copy Services

One of the main reasons for using Copy Services functions is to prepare for a
possible disaster by backing up, copying, and mirroring your data both at the local
(production) and remote sites.
Having a disaster recovery plan can ensure that critical data is recoverable at the
time of a disaster. Because most disasters are unplanned, your disaster recovery
plan must provide a way that allows you to recover your applications quickly, and
more importantly, to access your data. Consistent data to the same point-in-time
across all storage units is vital before you can recover your data at a backup
(normally your remote) site.
Most users use a combination of remote mirror and copy and point-in-time copy
(FlashCopy) features to form a comprehensive enterprise solution for disaster
recovery. In an event of a planned event or unplanned disaster, you can use
failover and failback modes as part of your recovery solution. Failover and failback
modes help to reduce the time that is required to synchronize remote mirror and
copy volumes after you switch between the local (or production) and the
intermediate or remote sites during planned and unplanned outages. Although
failover transmits no data, it changes the status of a device, and the status of the
secondary volume changes to a suspended primary volume. The Failback
command transmits data and can go in either direction depending on which device
the Failback command is issued to.
Recovery procedures that include failover and failback modes use remote mirror
and copy functions, such as Metro Mirror, Global Copy, Global Mirror,
Metro/Global Mirror, and FlashCopy.
Note: See the IBM System Storage DS8000 Command-Line Interface User's Guide for
Data consistency can be achieved using the following methods:
Manually using external software (without Global Mirror)
Automatically (with Global Mirror and FlashCopy)
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specific disaster recovery tasks.
If you use Metro Mirror, Global Copy, and FlashCopy functions to create a
consistent and restartable copy at your recovery site, you must do a
manual and periodic suspend operation at your local site. This means
using freeze and run commands together with external automated software
and then using the FlashCopy function to make a consistent copy of your
target volume for backup or recovery purposes. (Automation software is
not provided with the storage unit; it must be supplied by the user.)
Note: Freezing of the data is done at the same point-in-time across all
links and all storage units.
If you use a two-site Global Mirror or a three-site Metro/Global Mirror
configuration, the process to create a consistent and restartable copy at
your intermediate or remote site is done using an automated process, with
minimal or no interruption to your applications. Global Mirror operations
automate the process of continually forming consistency groups. It
combines Global Copy and FlashCopy operations to provide consistent
data at the remote site. A master storage unit (along with subordinate
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