Calculating the number of tables for each pair

ShadowImage User Guide
Version
9.8.7
Audience
anonymous
Part Number
MK-98RD9021-17

You can calculate the number of differential tables and pair tables that you will need for each pair.

Note: If a DP-VOL exceeds 4 TB, differential tables are placed in the hierarchy memory instead of the shared memory, and differential tables in the shared memory are not used. Therefore, it is not necessary to calculate the number of differential tables for DP-VOLs over 4 TB.
  1. Use the following formula: 
    Total number of the differential tables per pair = 
(volume capacity KB / 256) ÷ 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 capacity of the divided volume is 3,019,898,880 KB, the calculation is as follows: 

    (3,019,898,880 / 256) / 20,448 = 576.9014...

    Round up 576.9014 to the nearest whole number, 577.

  3. Use the following formula for calculating total number of the pair tables per pair: 
    Total number of the pair tables per pair = 
Total number of the differential tables per pair ÷ 36*
    * The number of differential tables used for each pair table.

    577 ÷ 36 = 16.0277...

    Round up 16.0277 to the nearest whole number and it will become 17.

    Therefore, total number of the pair tables per pair is 17 in this example.

    One or more pair tables can be used for each pair. However, the pair tables assigned to a pair cannot be used by a different pair until the pair is deleted.