HP XP Business Copy Software - Manual (Page 15)

If only BC uses differential tables, the following section describes how to calculate the number of
differential tables required for one BC pair, and the conditions you need to consider when calculating
the number of BC pairs that you can create.
NOTE:
You can use RAID Manager's inqraid command to query the number of differential tables required
when you create BC pairs. You can also use this command to query the number of unused differential
tables in the disk array. For more information about the inqraid command, see the
HP StorageWorks
RAID Manager XP user guide.
Calculating the number of differential tables for one BC pair
When you create a BC pair, the number of required differential tables changes according to the
emulation type of the volumes. Use the equations in
Table 2 to calculate the total number of differential
tables per pair.
Table 2 Total number of differential tables per pair
Equation Emulation type
Total number of differential tables per pair = [(X ÷ 48) + (Y x 15)] ÷ Z
•
(X): Volume capacity (KB)
1, 2
• (Y): Number of control cylinders associated with the emulation type (see Table 3 )
• (Z): Number of slots that can be managed by a differential table (61,312)
NOTE:
Round the result of the calculation up to the nearest whole number.
For example, if the volume's emulation type is OPEN-3, and it is not a custom volume,
the volume capacity (X) is the default volume size, 2,403,360 KB, and total number
of differential tables is calculated as follows:
[(2,403,360 ÷ 48) + (8 x 15)] ÷ 61,312 = 0.81860
When you round to the nearest whole number, the result is 1. Therefore, the total
number of differential tables for a pair is 1 when the emulation type is OPEN-3.
OPEN-3
OPEN-8
OPEN-9
OPEN-E
OPEN-L
XP Business Copy User Guide 15