Disaster recovery overview
Preparing for disaster recovery involves the following major steps:
1. Identify the volumes and groups that contain important files and data for
disaster recovery.
2. Create TrueCopy pairs, paying special attention to the options in P-VOL
Fence Level Settings to ensure that the system responds the way you
want in the event of a failure (see
Allowing I/O to the P-VOL after a split—
Fence Level options on page 3-10 ).
3. Install and configure host failover software between the local and remote
sites.
4. Establish file and database recovery procedures. These procedures for
recovering volumes due to control unit failure should already be in place.
5. Make sure that the host system at the primary site is configured to
receive sense information from the primary storage system (for example,
using CCI or SNMP). This should also be done at the remote site if a host
is connected to it.
Note: Procedures for disaster recovery involve releasing pairs. However,
when using CCI you can perform disaster recovery without releasing pairs. To
do this, when setting up TrueCopy, add a remote connection from the
secondary system to the primary system. Use the same path group ID as you
used from the primary to secondary system connection.
Remote copy and disaster recovery procedures are complex. Consult Hitachi
Data Systems customer support on sense-level settings and recovery
procedures.
Sense information shared between sites
When the primary system splits a TrueCopy pair due to an error condition,
the primary and secondary systems send sense information with unit check
status to the appropriate hosts. This is used during disaster recovery to
determine the consistency of the S-VOL, and must be transferred to the
secondary site via the host failover software.
File and database recovery
File recovery procedures for disaster recovery should be the same as those
used for recovering a data volume that becomes inaccessible due to control
unit failure.
TrueCopy does not provide a procedure for detecting and retrieving lost
updates. To detect and recreate lost updates, you must check other current
information (for example, database log file) that was active at the primary
system when the disaster occurred.
The detection and retrieval process can take some time. Your disaster
recovery scenario should be designed so that detection and retrieval of lost
9-2
Disaster recovery
Hitachi TrueCopy® User Guide for Hitachi Virtual Storage Platform Gx00 and Fx00 Models
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