HP XP7 Storage - Manual (Page 29)

Calculating maximum number of pairs
NOTE: In the calculations below, note the following:
•
ceil () indicates that the value between the parentheses should be rounded up to the nearest
integer.
To calculate the number of cylinders
Use one of the following formulas:
•
For pairs created with a Virtual LVI volume or THP V-VOL and emulation type 3390:
The number of cylinders = (ceil ( (ceil (Number of logical blocks
/ 116) ) / 15))
•
For pairs created without a Virtual LVI volume or THP V-VOL, find the number of cylinders for
your system’s emulation type in the following table.
Number of cylinders Emulation type
1,113 3390-1
2,226 3390-2
3,339 3390-3
10,017 3390-9
262,668 3390-A
32,760 3390-L
65,520 3390-M
To calculate the number of required bitmap areas:
Use the following formula
ceil((number of cylinders x 15) / 122,752) )
where:
•
number of cylinders x 15 indicates the number of slots
•
122,752 is the number of slots that a bitmap area can manage
NOTE: Doing this calculation for multiple volumes can result in inaccuracies. Perform the
calculation for each volume seperately, then total the bitmap areas. The following examples
show correct and incorrect calculations. Two volumes are used: one of 10,017 cylinders and
another of 32,760 cylinders
Correct calculation
ceil ((10,017 x 15) / 122,752) = 2
ceil ((32,760 x 15) / 122,752) = 5
Total: 7
Incorrect calculation
10,017 + 32,760 = 42,777 cylinders
ceil ((42,777 x 15) / 122,752) = 6
To calculate the maximum number of pairs
Planning pair volumes 29