Calculating the numbers of differential and pair tables for each pair

TrueCopy® User Guide
Version
9.8.5
Audience
anonymous
Part Number
MK-98RD9022-16

If a DP-VOL exceeds 4 TB, the differential tables are placed in the hierarchy memory instead of the shared memory, and the 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. Calculate how many differential tables are required for each pair.
    Use the following formulas:
    number-of-differential-tables-for-expansion = number-of-differential-tables-after-expansion - number-of-differential-tables-before-expansion
    number-of-differential-tables-per-pair = ceiling ((volume-capacity [KB] / 256) / 20,448)

    Ensure that the ceiling value enclosed in the parenthesis () is rounded up to the next integer.

  2. Calculate how many pair tables are required for each pair.
    Use the following formulas:
    number-of-pair-tables-for-expansion = number-of-pair-tables-after-expansion - number-of-pair-tables-before-expansion
    number-of-pair-tables-per-pair = ceiling ((number-of-pair-tables-per-pair / 36)

    Ensure that the ceiling value enclosed in the parenthesis () is rounded up to the next integer.

  3. Verify that the following numbers do not exceed the maximum number allowed on the storage system.
    • The total numbers of current pair tables and pair tables required for expanding the capacity
    • The total numbers of current differential tables and differential tables required for expanding the capacity

    You can check the numbers of differential and pair tables in the Local Replication window.