HP XP Continuous Access Software - Manual (Page 51)

Duplicate Volumes
Since the contents of the primary data volume and secondary data volume of an XP Continuous
Access Journal pair are identical, the secondary data volume can be considered a duplicate of
the primary data volume. Since the host operating system does not allow duplicate volumes, the
host system administrator must take precautions to prevent system problems related to duplicate
volumes. You must define the XP Continuous Access Journal secondary data volume so it does not
auto-mount or come online on the same host at the same time as the primary data volume (see
WARNING).
XP Continuous Access Journal does not allow the secondary data volume to be online (except while
the pair is split). If the secondary data volume is online, the XP Continuous Access Journal paircreate
operation fails.
WARNING: If the XP Continuous Access Journal secondary data volumes are physically attached
to the same host server(s) as the XP Continuous Access Journal primary data volumes, the following
problem can occur:
•
When an XP Continuous Access Journal pair is released, the old secondary data volume is
usually offline. If the host is then restarted, the system administrator may be offered both
volumes and asked which volume should be left offline. This can be confusing and prone to
error.
•
If the XP Continuous Access Journal secondary data volumes and primary data volumes are
connected to the same host(s), HP strongly recommends that the secondary data volumes are
defined to remain offline to avoid this problem.
Installing the Hardware
Initial installation of the XP Continuous Access Journal hardware is performed by the user and the
HP service representative. To install the hardware required for XP Continuous Access Journal
operations:
1. User: Identify the locations of the XP Continuous Access Journal primary and secondary data
volumes (primary data volumes and secondary data volumes) so that the XP Continuous Access
Journal hardware can be installed and configured properly.
2. HP Service Representative: Make sure that the primary storage system(s) and secondary storage
system(s) are configured for Remote Web Console operations (for example, the SVP is
connected to a LAN). See the HP StorageWorks XP24000/XP20000 Remote Web Console
User Guide for information and instructions on setting up Remote Web Console operations.
3. HP Service Representative: Make sure that the primary storage systems and secondary storage
systems are properly configured for XP Continuous Access Journal operations. For example,
for cache and NVS see
“Cache and Nonvolatile Storage (NVS)” (page 50) . Make sure that
the desired system option modes are enabled; see “Metadata Information” (page 25) . Make
sure that adequate cache is installed and available for XP Continuous Access Journal operations.
You must also consider the amount of Cache Residency Manager data to be stored in cache
when determining the required amount of cache.
4. HP Service Representative: Make sure that the primary storage systems are configured to report
sense information to the host(s). The secondary storage systems should also be attached to a
host server to enable reporting of sense information in case of a problem with a secondary
data volume or secondary storage system. If the remote site is unattended, the secondary
storage systems should be attached to a host server at the primary site so that the system
administrator can monitor the operational condition of the secondary storage systems.
5. HP Service Representative: If power sequence control cables are used, set the power select
switch for the cluster to LOCAL to prevent the primary storage system from being powered off
by the host. Also make sure that the secondary storage system is not be powered off during
XP Continuous Access Journal operations. See
“Managing Power for Storage Systems and
Installing the Hardware 51