Duplicate volumes, Port configurations, Duplicate volumes port configurations – HP XP Continuous Access Software User Manual
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paircreate operation fails. The remote array cache should be configured to adequately support XP
Continuous Access Journal remote copy workloads and local workload activity.
Duplicate volumes
Because the contents of an XP Continuous Access Journal pair's primary and secondary data
volumes are identical, the secondary data volume can be considered a duplicate of the primary
data volume. Because 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 to the same host at the same time as the primary data volume.
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.
CAUTION:
If the XP Continuous Access Journal secondary data volume is physically attached to
the same host servers as the XP Continuous Access Journal primary data volumes, the following
problem can occur:
•
When an XP Continuous Access Journal pair is deleted, if the host is then restarted, the system
administrator might be offered both volumes and asked which volume should be left offline.
This can be confusing and is prone to error.
If the XP Continuous Access Journal secondary and primary data volumes are connected to the
same hosts, HP strongly recommends that you define secondary data volumes to remain offline to
avoid this problem.
Port configurations
When configuring a system for using XP Continuous Access Journal, ensure that ports are configured
correctly.
and
explain cases of illegal port configurations. For
example, as the first row of
indicates, if you use the CL1-A port as an RCU
target port in the XP Continuous Access Journal primary site, you must not use the CL1-A or CL5-A
port as a target port in the XP Continuous Access Journal primary site. Also, if you configure a
system in a 3-data center (3DC) cascading configuration (see
Combining XP Continuous Access
Journal with XP Continuous Access (3DC cascading configuration)
) and you use the CL1-A port as
an RCU target port in the XP Continuous Access Journal primary site, you must not use the CL1-A
or CL5-A port as an RCU target port in the XP Continuous Access secondary site. As these examples
indicate, you must avoid using illegal combinations of an RCU target port in the XP Continuous
Access Journal primary site and a target port in the XP Continuous Access Journal primary site.
Also, when configuring a system in a 3DC cascading configuration, you must avoid using illegal
combinations of an RCU target port in the XP Continuous Access Journal primary site and an RCU
target port in the XP Continuous Access secondary site.
If you use illegal port combinations, XP Continuous Access Journal remote copy operations are
likely to be suspended due to failures. If an XP Continuous Access Journal remote copy operation
is suspended due to a failure, the following problems occur and the remote copy operation cannot
be performed:
•
The primary array cannot read data from the primary data volume.
•
In a system with a 3DC cascading configuration, the intermediate site cannot read data from
a volume used as both an XP Continuous Access Synchronous secondary volume and an XP
Continuous Access Journal primary data volume.
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XP Continuous Access Journal operations requirements and restrictions