Planning Pair Volumes; Planning Number Of Pairs - HP XP P9500 User Manual

Table 2 The volumes and capacities to be counted as the usage capacity of Business Copy (continued)
Volume to be counted
Program product
Snapshot
The word "Normal-VOL" in the above table means an internal volume or an external volume that
is not specified as a Thin Provisioning volume. Besides, external volumes refer to internal volumes
that are mapped to volumes in external storage systems by External Storage.THP V-VOL is a virtual
volume that is used in Thin Provisioning.
When Business Copy and Snapshot share volumes, the capacity of the shared volumes is added
to Business Copy usage capacity only once.

Planning pair volumes

You must create volumes for P-VOLs and S-VOLs prior to creating pairs. Review system requirements
for pair volumes in
Before you create a pair, you can reserve a volume as an S-VOL. This insures that no I/O
occurs in the reserved volume before creating a pair. Reserved volumes may only be used as
S-VOLs.
If you use , you can place a group of pairs in a consistency group. Using the consistency
group, you can perform pair operations on all the pairs in the group at the same time, including
the At-Time Split operation with which you can specify the split time. See the HP P9000 RAID
Manager User Guide for information on setting up consistency groups and performing pair
operations.

Planning number of pairs

This section provides instructions for calculating the number of system resources required for one
Business Copy pair. With this information you can calculate the maximum number of pairs.
When you create pairs, differential tables (tables managing differential bitmaps) and pair tables
are required. These must be available in sufficient number to handle all the pairs you will create.
The number of differential and pair tables that are present in the system depends on additional
shared memory that is installed. Therefore, you must insure that you have sufficient additional
shared memory to handle the number of pairs.
The following table shows the number of differential and pair tables and the number of volumes
allowed per additional shared memory. The maximum number of pairs is half the number of volumes
shown, when P-VOLs and S-VOLs are in a one-to-one relationship.
For example, if additional shared memory is not installed, since the number of volumes is 16,384,
then the number of pairs you can create is 8,192. This example assumes one S-VOL per P-VOL. If
there are more S-VOLs than P-VOLs, then the number of allowed pairs decreases.
However, for Extension 1 and Extension 2, the maximum number of pairs is 16,384, regardless
of the total number of system volumes.
12 Requirements and planning
The kind of the volumes
Reserved-VOL
P-VOL
S-VOL
Table 1 (page 10). Also, the following options can be used:
Capacity to be counted
Normal-VOL or THP
V-VOL
THP V-VOL Pool capacity that the
volume is using
Normal VOL Volume capacity
THP V-VOL Pool capacity that the
volume is using
Normal VOL Volume capacity
THP V-VOL Pool capacity that the
volume is using
Normal VOL Volume capacity