Calculate the number of tables for each pair

ShadowImage User Guide for VSP One Block

Version

10.5.x

Audience

anonymous

Part Number

MK-23VSP1B014-06

ft:lastEdition

2026-05-04

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.

Use the following formula to calculate the total number of the differential tables per pair:
```
total-number-of-differential-tables-per-pair = 
(volume capacity (KB)/256) / 20,448*
```
* This is the number of slots that a differential table can manage.
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.
Use the following formula to calculate the total number of pair tables per pair:
```
total-number-of-pair-tables-per-pair = 
total-number-of-differential-tables-per-pair / 36*
```
* This is the number of differential tables used for each pair table.

577 / 36 = 16.0277

Round up 16.0277 to the nearest whole number, 17.

Therefore, the total number of 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.