Planning And Procedures For Disaster Recovery; Disaster Recovery Overview; Transfer Sense Information Between Sites; File And Database Recovery - HP StorageWorks P9000 User Manual

9 Planning and procedures for disaster recovery

This chapter discusses and provides instructions for using Continuous Access Synchronous for
disaster recovery.

Disaster recovery overview

The major steps in preparing for disaster recovery are:
1. Identify the volumes and groups that contain important files and data for disaster recovery.
2. Create Continuous Access Synchronous 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 the prerequisites in
3. Install and configure host failover software between the main 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 P9500 primary system (for example, using RAID Manager or SNMP). This should
also be done at the secondary site if a host is connected to it.
Remote copy and disaster recovery procedures are inherently complex. Consult your HP account
team on sense-level settings and recovery procedures.

Transfer sense information between sites

When the primary system split a Continuous Access Synchronous pair due to an error condition,
the primary and secondary systems send sense information with unit check status to the appropriate
host(s). This is used during disaster recovery to determine the currency of the S-VOL, and must be
transferred to the remote site via the host failover software.

File and database recovery

File recovery procedures are necessary in such cases. These procedures should be the same as
those used for recovering a data volume that becomes inaccessible due to control unit failure.
Continuous Access Synchronous 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 updates is performed after the application has
been started at the secondary site.
You should prepare for file and database recovery using files for file recovery (for example,
database log files that have been verified as current).

Switch operations to the secondary site

If a disaster or failure occurs at the primary site, the first disaster recovery activity is to switch your
operations to the secondary site. S-VOLs are recovered individually based on the pair status and
P-VOL fence level information for each pair.
Procedure 22 To switch operations to the secondary site
1. Record the pair status and fence level of each S-VOL.
2. Analyze the currency of the S-VOLs, based on its pair status and P-VOL fence level setting.
See "Analyze S-VOL currency" (page
further analysis is required. This can be done using sense information transferred via host
failover, or by comparing the contents of an S-VOLs with other files confirmed to be current
"Create pairs" (page 46)).
66). For pairs with P-VOL fence level setting of Never,
Disaster recovery overview 65