HP XP P9500 Storage - Manual (Page 15)

To calculate the number of differential and pair tables for emulation types other than OPEN-V
Total number of differential tables per pair = (volume capacity KB ÷
48) + (number of the control cylinders* Ч 15) ч (20,448**)
* See the following table.
** Number of slots that can be managed by a differential table
Round up the total number to the nearest whole number. For example, if the number of the cylinders
of the divided volume is 2,403,360 KB, the calculation of the total number of the differential tables
is as follows:
(2,403,360 ч 48 + 8 Ч 15) ч 20,448 = 2.4545...
Rounding up 2.4545 to the nearest whole number changes it to 3. In this example, the total number
of the differential tables for one pair is 3. Because one pair table is used for up to 36 differential
tables, the total number of the pair tables for a pair in this example is 1.
To calculate the number of differential and pair tables for OPEN-V
Total number of the differential tables per pair = (volume capacity KB
ч 256) ч 20,448*
* Number of the slots that can be managed by a differential table
Round up the total number to the nearest whole number. For example, if the number of the cylinders
of the divided volume is 3,019,898,880 KB, the calculation of the total number of the differential
tables is as follows.
(3,019,898,880 ч 256) ч 20,448 = 576.9014...
Rounding up 576.9014 to the nearest whole number changes it to 577. In this example, the total
number of the differential tables for one pair is 577. Because one pair table is used for up to 36
differential tables, the total number of the pair tables for a pair is 17. (Only OPEN-V can use more
than one pair table per pair.)
Table 2 Control cylinders per emulation type
Number of control cylinders Emulation type
8 (5,760KB) OPEN-3
27 (19,440KB) OPEN-8, OPEN-9
19 (13,680KB) OPEN-E
9 (6,480KB) OPEN-K
7 (5,040KB) OPEN-L
0 (0KB) OPEN-V
If the volume is divided by VLL, use the volume capacity after the division.
NOTE: You cannot perform VLL operations on OPEN-L volumes.
Having determined the number of differential and pair tables required per pair on your storage
system, you can now calculate the maximum number of pairs.
Calculating maximum number of pairs
Finding the number of pairs that can be created on your system depends on whether you use LUSE
volumes or not. Two calculations are provided below, one without LUSE, and one with LUSE.
To calculate the maximum number of pairs allowed on your system without LUSE volumes
Use the following formula:
Σ {(α) x (the number of BC pairs)} ≤ (β) and Σ {(γ) x (the number of BC pairs)} ≤ (δ)
Planning pair volumes 15