HP XP7 Storage - Manual (Page 95)

9 Disaster recovery
This chapter discusses disaster recovery.
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 Continuous Access Synchronous Z 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” (page 36) ).
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 local site is configured to receive sense information from
the XP7 primary system (for example, using 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 Business
Continuity Manager you can perform disaster recovery without releasing pairs. To do this, when
setting up Continuous Access Synchronous Z, add remote paths between the secondary system
Initiator ports and primary system RCU Target ports. Then add a remote connection from the
secondary system CU to the primary system CU.
Remote copy and disaster recovery procedures are complex. Consult your HP account team on
sense-level settings and recovery procedures.
Sense information shared between sites
When the primary system splits a Continuous Access Synchronous Z pair due to an error condition,
the primary and secondary system 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 remote site via the host failover software.
If the host system supports IBM PPRC and receives PPRC compatible sense information related to
a Continuous Access Synchronous Z pair, the host OS will perform the following actions:
1.
Temporarily split all application I/O operations to the P-VOL.
2. Enter an IEA491E message in the system log (SYSLOG) that indicates the time that the P-VOL
was split. Make sure that the system log is common to both the local and remote operating
systems.
3. Place specific information about the failure (SIM) in the SYS1.LOGREC dataset for use by
service personnel. See
“Service Information Messages (SIMs)” (page 113) for more information
about SIM.
4. Wait for the IEA491E message to reach the secondary system.
5. Resume all host application I/O operations to the P-VOL. If the P-VOL fence level setting does
not allow subsequent updates, the MCU will return a unit check for all subsequent write I/O
operations, and the application will terminate.
Make sure that the MCUs and RCUs are configured to report the service level SIMs to the host.
Select the Services SIM of Remote Copy = Report setting on the Change CU Options window.
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.
Disaster recovery overview 95