After you determine the necessary number of differential and pair tables, determine whether
the planned number of pairs can be created.
The number of differential and pair tables for a pair depends on the volume capacity.
-
Calculate how many differential tables are required for the planned number of pairs:
number-of-differential-tables-per-pair × planned-number-of-pairs
-
Calculate how many pair tables are required for the planned number of pairs:
number-of-pair-tables-per-pair × planned-number-of-pairs
-
Verify that the storage system has enough differential tables and pair tables available.
- The number of differential tables calculated in step 1 must not exceed the number of available differential tables
- The number of pair tables calculated in step 2 must not exceed the number of available pair tables
Note:
- When creating ShadowImage pairs with multiple
volumes that have different capacities, apply the total numbers of differential
tables calculated for each volume.
- When creating ShadowImage pairs with multiple
volumes that have different capacities, apply the total numbers of pair tables
calculated for each volume.
- The number of available differential tables and pair tables depends
on the amount of installed shared memory.
Example
if you plan to create 20 pairs in a storage system that has 57,600 differential tables, use the following calculation:
577 × 20 = 11,570, which is ≤ 57,600
If the capacity of the volume is 3,019,898,880 KB, you will need 577 differential tables and 17 pair tables.
Apply these numbers to the following formula:
577 × 20 = 11,570 ≤ 57,600
and
17 × 20 = 340 ≤ 8,192
Therefore, you can create 20 pairs.