HP XP P9500 Storage - Manual (Page 16)

where:
•
(α): Required number of differential tables per pair (per previous calculation).
•
(β): Number of differential tables available in the system ( Table 1 (page 14) ).
•
(γ): The required number of pair tables per pair (per previous calculation).
•
(δ): The number of pair tables available in the system ( Table 1 (page 14) ).
For example, if you are to create 10 pairs of OPEN-3 volumes and 20 pairs of OPEN-V volumes
in a storage system that has 26,176 differential tables, you can use the equation as follows:
If the emulation type is OPEN-3 and the capacity of the volume is 2,403,360 kB, 3 differential
tables and a pair table is required for a pair. If the emulation type is OPEN-V and the capacity of
the volume is 3,019,898,880 kB, 577 differential tables and 17 pair tables are required for a
pair.
If you apply these numbers in equation:
3 x 10 + 577 x 20 = 11,570 less-than-or-equal-to 26,167 and also
1 x 10 + 17 x 20 = 350 less-than-or-equal-to 8,192
Thus, 10 pairs of OPEN-3 volumes and 20 pairs of OPEN V volumes can be created.
To calculate the maximum number of pairs allowed on your system with LUSE volumes
Σ[Σ {(α) x (the number of the volumes that forms LUSE volumes)} x (the number of BC pairs)] ≤ (β)
and also
Σ[Σ {(γ) x (the number of the volumes that forms LUSE volumes)} x (the number of BC pairs)] ≤ (δ)
where:
•
(α): Required number of differential tables that forms a LUSE volume.
When you use LUSE volumes, each volume forming the LUSE volume uses the differential
tables. For example, if you create a BC pair using LUSE volumes, which are created by
combining two OPEN-V volumes, you need differential tables for two OPEN-V pairs.
•
(β): Number of differential tables available in the system ( Table 1 (page 14) ).
•
(γ): The required number of pair tables for each volume that forms a LUSE volume.
•
(δ): The number of pair tables available in the system ( Table 1 (page 14) ).
For example, if you are to create 10 pairs of LUSE volumes consisting respectively of three OPEN-3
volumes in a storage system that has 26,176 differential tables, you can use the equation condition
as follows:
When the emulation type is OPEN-3, and if the capacity of the volume is 2,403,360 kB, the
number of differential tables required for a pair is 3, and the number of pair tables required for a
pair will be 1.
If you apply this number to the above-mentioned equation:
(3 x 3) x 10 = 90 <= 26,176
and also
(1 x 3) x 10 = 30 <= 8,192
Therefore, you can see that 10 BC pairs, which are formed by three OPEN-3, volumes can be
created.
Organizing volumes into P-VOLs and S-VOLs
Before creating pairs, you must prepare volumes for BC. The following table provides an example
of volume information to prepare volumes.
16 Requirements and planning