HP XP Racks - Manual (Page 14)

• Use the following formula:
The number of differential and pair tables your XP7 storage system
needs =< (the total number of differential and pair tables in the
XP7 storage system - the number of tables other software applications
are using, such as Compatible FlashCopy)
Calculating the number of tables for emulation types that are not OPEN-V
You can calculate the number of differential and pair table you will need for a volume that has an
emulation type other than OPEN-V.
1.
Use the following formula:
Total number of differential tables per pair = (volume capacity KB
÷ 48) + (number of the control cylinders* Ч 15) ч (20,448**)
* See the table that shows the control cylinders per emulation type in the following section.
** 20,488 is the number of slots that a differential table can manage.
2. 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, use the following
calculation to get the total number of the differential tables:
(2,403,360 ч 48 + 8 Ч 15) ч 20,448 = 2.4545...
Round up 2.4545 to the nearest whole number, 3. In this example, you will need three differential
tables for the pair and one pair table.
Calculating the number of tables for OPEN-V emulation types
You can calculate the number of differential and pair tables you will need for a volume that has
an OPEN-V emulation type.
NOTE: Only the OPEN-V emulation type can use more than one pair table per pair.
1. Use the following formula:
Total number of the differential tables per pair = (volume capacity
KB ч 256) ч 20,448*
* The number of slots that a differential table can manage.
2. 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, use the
following calculation to get the total number of the differential tables:
(3,019,898,880 ч 256) ч 20,448 = 576.9014...
Round up 576.9014 to the nearest whole number, 577. In this example, you will need 577
differential tables and 17 pair tables.
The following table shows the 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
14 Business Copy system requirements and planning