HP XP P9500 Storage - Manual (Page 29)

Maximum number of pairs allowed
P9500 has a limit on the number of pairs that can be created. Therefore, it is necessary to calculate
the maximum number of pairs on the P9500 storage system. The maximum number is limited
according to the following:
1.
The number of cylinders in the volumes, which must be calculated.
2. The number of bitmap areas required for Continuous Access Journal data and journal volumes.
This is calculated using the number of cylinders.
3. The maximum number of pairs that can be created, calculated using the number of required
bitmap areas.
CAUTION: The bitmap areas that are used for Continuous Access Journal are also used for
Continuous Access Journal Z, Continuous Access Synchronous, Continuous Access Synchronous
Z, and External Storage Access Manager. If you use Continuous Access Journal with Continuous
Access Journal Z, Continuous Access Synchronous, and Continuous Access Synchronous Z, use
the total number of each pair’s bitmap areas to calculate the maximum number of pairs. In addition,
if Continuous Access Journal and Continuous Access Synchronous share the same volume, use the
total number of both pairs regardless of whether the shared volume is primary or secondary.
Calculating maximum number of pairs
NOTE: In the calculations below, ceil() indicate that the value between the parentheses should
be rounded up to the nearest integer.
To determine the number of cylinders
The number of cylinders according to the emulation type are listed below.
Table 5 Number of cylinders per emulation type
Number of cylinders Emulation type
3,339 3380-3
3,339 3390-3, 3390-3R
10,017 3390-9
32,760 3390-L
65,520 3390-M
To calculate the number of required bitmap areas:
Use the following formula
Required number of bitmap areas = (ceil((number of cylinders x 15)
122,752) )
where:
“number of cylinders x 15” indicates the number of slots
122,752 = the number of slots that a bitmap area can manage
To calculate the maximum number of pairs that can be created
The maximum number of pairs you can create is defined by the following:
•
The number of LDEVs in the storage system
Planning pair volumes 29