HP XP7 Storage - Manual (Page 24)

You will have two options for specifying how the system matchs S-VOLs to P-VOLs.
- Interval: The interval you specify will be skipped between LDEV numbers in the secondary
system.
For example, suppose you specify LU 01 as the initial (base) S-VOL, and specify 3 for Interval.
This results in secondary system LDEV 04 being assigned to the next P-VOL, 07 assigned to
the subsequent P-VOL, and so on. To use Interval, you set up secondary system LDEV numbers
according to the interval between them.
- Relative Primary Volume. The difference is calculated between the LDEV numbers of two
successive P-VOLs. S-VOLs are assigned according to the closest LUN number.
For example, if the LUN numbers of three P-VOLs are 1, 5, and 6; and you set LUN numbers
for the initial S-VOL (Base Secondary Volume) at 2, the LUN numbers of the three S-VOLs will
be set at 2, 6, and 7, respectively.
•
You can create a Cnt Ac-J pair using a Continuous Access Synchronous initial copy, which
takes less time. To do this, system option 474 must be set on the primary and secondary
systems. Also, a script is required to perform this operation. For more on system option 474
and how to do this operation, see
“System option modes ” (page 30) .
•
Cnt Ac-J supports the Virtual LUN feature, which allows you to configure custom LUs that are
smaller than standard LUs. When custom LUs are assigned to a Cnt Ac-J pair, the S-VOL must
have the same capacity as the P-VOL. For details about Virtual LUN feature, see the HP XP7
Provisioning for Open Systems User Guide.
•
Identify the volumes that will become the P-VOLs and S-VOLs. Note the port, group ID (GID),
and LUN of each volume. This information is used during the initial copy operation.
•
You can create multiple pairs at the same time. Review the prerequisites and steps in “Creating
the Cnt Ac-J initial copy ” (page 43) .
•
When you create a Cnt Ac-J pair, you will have the option to create only the relationship,
without copying data from P-VOL to S-VOL. You can use this option only when data in the two
volumes is identical.
Maximum number of pairs allowed
You can create up to 65,280 pairs on a XP7 system. The maximum number for your system is
limited by:
1.
The number of cylinders in the volumes, which must be calculated.
2. The number of bitmap areas required for Continuous Access Journal data and journal volumes.
This is calculated using the number of cylinders.
CAUTION: The bitmap areas that are used for Continuous Access Journal are also used for
Continuous Access Journal Z, Continuous Access Synchronous, and Continuous Access Synchronous
Z. If you use Cnt Ac-J with any of these products, use the total number of each pair’s bitmap areas
to calculate the maximum number of pairs. In addition, if Cnt Ac-J and Cnt Ac-S share the same
volume, use the total number of both pairs regardless of whether the shared volume is primary or
secondary.
24 Planning volumes, XP7 systems