HP XP Continuous Access Software - Manual (Page 97)

Continuous Access XP user guide for the XP1024/XP128 97
Continuous Access XP disaster recovery operations
Preparing for disaster recovery
The type of disaster and status of Continuous Access XP volume pairs determines the best approach for
disaster recovery. For example, if all Continuous Access XP volume pairs are in the PAIR state when a
total system failure occurs at a single point in time, S-VOLs are current and recovery is straightforward.
Unfortunately, some disasters are not so “orderly” and involve intermittent or gradual failures occurring
over a longer period of time. You should anticipate and plan for all types of failures and disasters.
Major steps in preparing for disaster recovery are:
1. Identify volumes and volume groups containing important files and data for disaster recovery. In
addition to supporting Continuous Access XP remote copy operations as well as RAID Manager
commands, the disk array provides battery-backed nonvolatile duplexed cache, full hardware
redundancy, dynamic sparing, and an advanced RAID-5 implementation to ensure full data integrity if
a sudden power outage or other failure occurs.
2. Install Continuous Access XP. Install the Command View XP management station or use XP Remote
Web Console to establish Continuous Access XP operations for volumes and groups identified in
step 1 . Select the proper CU images to access the volumes. See ” Preparing for Continuous Access XP
operations ” on page 30 for instructions on installing Continuous Access XP. See ” Performing
Continuous Access XP configuration operations ” on page 53 for instructions on performing
Continuous Access XP configuration operations. See ” Performing Continuous Access XP pair
operations ” on page 78 for instructions on performing Continuous Access XP pair operations.
3. Use the appropriate combination of Continuous Access XP options for disaster recovery:
• Continuous Access XP Async offloading timer option (see ”
Asynchronous copy option ” on
page 70) and copy pending timeout group option (see ” Modifying consistency group options (CT
Group Option) ” on page 69). Use the copy pending timeout group option to limit the time duration
during which updates may be lost.
NOTE: When channel extenders are used for Continuous Access XP Async, set the offloading
timer to 35 seconds or less to avoid affecting host I/O performance.
• Continuous Access XP Async Error Level pair option and Continuous Access XP Synchronous P-VOL
Fence Level pair option (see ” Creating Continuous Access XP volume pairs (Paircreate) ” on
page 81).
4. Establish file and database recovery procedures. These procedures should already be established for
recovering volumes that become inaccessible due to control unit failure.
5. Ensure that the host system at the primary site is configured to receive sense information from MCUs
(via RAID Manager or SNMP).
6. Install and configure host failover software between the main and remote sites. Host failover capability
is essential if you use the P-VOL fence-level setting of S-VOL Status or Never for any Continuous Access
XP volume pairs.
Considering the P-VOL fence-level setting
The P-VOL fence-level setting (see ” Creating Continuous Access XP volume pairs (Paircreate) ” on page 81)
for each Continuous Access XP Synchronous volume pair determines whether the P-VOL is fenced when
Continuous Access XP remote copy operations fail. Table 19 summarizes the effect of the fence-level
setting on a Continuous Access XP Sync P-VOL.