HP XP P9500 Storage - Manual (Page 23)

Procedure 1 To calculate the maximum number of pairs
1. Calculate the number of cylinders.
1.
Calculate the system’s number of logical blocks, which is the volume’s capacity measured
in blocks.
Number of logical blocks = Volume capacity (bytes) / 512
2. Calculate the number of cylinders:
For OPEN-3, OPEN-8, OPEN-9, OPEN-E, OPEN-L, OPEN-K:
Number of cylinders = ceil ( (ceil (Number of logical blocks /
96) ) / 15)
For OPEN-V.
Number of cylinders = ceil ( (ceil (Number of logical blocks /
512) ) / 15)
2. Calculate the number of bitmap areas per volume.
In the following calculation, differential data is measured in bits. 122,752 bits is the amount
of differential data per bitmap area.
For OPEN-3, OPEN-8, OPEN-9, OPEN-E, OPEN-L, OPEN-K, and OPEN-V:
Number of bitmap areas = ceil ( (Number of cylinders x 15) / 122,752)
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
Planning for pairs and pair volumes 23