HP XP Racks - Manual (Page 15)

Determining the number of tables required for Business Copy
You can query the number of differential tables that are required to create Business Copy (BC/SS)
pairs.
•
Run the following RAID Manager command:
inqraid
For more information about running this command, see the HP XP7 RAID Manager User Guide.
Determining the number of used tables in the storage system
You can query the number of differential tables that are not used in the XP7 storage system.
•
Run the following RAID Manager command:
inqraid
For more information about running this command, see the HP XP7 RAID Manager User Guide.
Calculating the maximum number of BC pairs
You can calculate the maximum number of BC pairs your XP7 storage system can support. In the
calculation, you use the results of calculating the number of differential and pair table.
•
Use the following formula:
Σ {(α) x (the number of BC pairs)} ≤ (β) and Σ {(γ) x (the number
of BC pairs)}
≤ (δ)
where:
•
(α): The required number of differential tables per pair (per previous calculation).
•
(β): The number of differential tables available in the system.
For more information about differential tables, see “Tables and installed shared memory”
(page 13) .
•
(γ): The required number of pair tables per pair.
For more information about determining the number of differential and pair tables your
storage system needs to create BC pairs, see
“Determining capacity of BC pairs in XP7
workflow” (page 12) .
•
(δ): The number of pair tables available in the system.
For more information about pair tables, see “Tables and installed shared memory”
(page 13) .
NOTE: The values for (β) and (δ) in the calculation are dependent on the amount of installed
shared memory.
For more information about installed shared memory, see “Tables and installed shared memory”
(page 13) .
For example, if you plan to create 10 BC pairs of OPEN-3 volumes and 20 BC pairs of OPEN-V
volumes in a XP7 storage system that has 57,600 differential tables, use the following calculation:
3 x 10 + 577 x 20 = 11,570 , which is <= 57,600
If the emulation type is OPEN-3 and the capacity of the volume is 2,403,360 kB, you will need
three differential tables and one pair table.
If the emulation type is OPEN-V and the capacity of the volume is 3,019,898,880 kB, you will
need 577 differential tables and 17 pair tables.
Apply these numbers to the following formula:
Determining capacity of BC pairs in XP7 workflow 15