IBM DS8900F, Введение и руководство по планированию

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• Metro Mirror indicator feature numbers 75xx and 0744 and corresponding DS8000 series function
authorization (2396-LFA MM feature numbers 75xx)
• Global Mirror indicator feature numbers 75xx and 0746 and corresponding DS8000 series function
authorization (2396-LFA GM feature numbers 75xx).
Global Copy is a non-synchronous long-distance copy option for data migration and backup.
Disaster recovery through Copy Services
Through Copy Services functions, you can prepare for a disaster by backing up, copying, and mirroring
your data at local 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 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 can reduce the synchronization time of remote mirror and copy volumes after you
switch between local (or production) and intermediate (or remote) sites during an outage. 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 device that initiates the failback command determines the
direction of the transmitted data.
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, Multiple Target PPRC, and FlashCopy.
Note: See the IBM DS8000 Command-Line Interface User's Guide for specific disaster recovery tasks.
Data consistency can be achieved through the following methods:
Manually using external software (without Global Mirror)
You can use Metro Mirror, Global Copy, and FlashCopy functions to create a consistent and restartable
copy at your recovery site. These functions require a manual and periodic suspend operation at the
local site. For instance, you can enter the freeze and run commands with external automated
software. Then, you can initiate a FlashCopy function to make a consistent copy of the target volume
for backup or recovery purposes. Automation software is not provided with the storage system; it
must be supplied by the user.
Note: The
freeze operation occurs at the same point-in-time across all links and all storage
systems.
Automatically (with Global Mirror and FlashCopy)
You can automatically create a consistent and restartable copy at your intermediate or remote site
with minimal or no interruption of applications. This automated process is available for two-site
Global Mirror or three-site Metro / Global Mirror configurations. 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 storage units) internally manages data consistency through 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 session-grouped volumes across multiple storage
systems. Consistency groups 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.
If a disaster occurs at a local site with a two or three-site configuration, you can continue production
on the remote (or intermediate) site. The consistent point-in-time data from the remote site
consistency group enables recovery at the local site when it becomes operational.
50 IBM DS8900F: DS8900F Introduction and Planning Guide