Calculating and assigning pool capacity

Thin Image User Guide

Version

9.8.6

Audience

anonymous

Part Number

MK-98RD9020-16

Use these formulas to calculate and assign pool capacity.

Use the following formula to calculate the capacity of the snapshot data that you can store in the Thin Image pool:

Capacity of the snapshot data that you can store in the pool = 
Total capacity of pool-VOLs in the pool - Capacity of V-VOL management areas

The capacity of V-VOL management areas is 3% of the pool capacity.

Note: The capacity of V-VOL management areas varies depending on the P-VOL capacity and the number of pairs. Use the following formula to calculate the capacity of V-VOL management areas for each P-VOL of a Thin Image pair. To calculate the capacities of V-VOL management areas for all Thin Image pairs, add up the capacity calculated for each P-VOL.

Capacity of V-VOL management areas for each P-VOL (MB) ＝ (4 + ceiling ((2 × Updated volume type × Number of pairs + 64) × (Volume capacity (MB) ÷ 3145728 (MB))))× 42

Details:

Updated volume type: Set to 1 or 2 depending on the volumes to be updated:

Set to 1 if only P-VOLs are updated.
Set to 1 if only S-VOLs are updated.
Set to 2 if both P-VOLs and S-VOLs are updated.

Number of pairs: Number of the S-VOLs for each P-VOL

Volume capacity: P-VOL capacity (MB)

Ceiling: The value enclosed in ceiling( ) must be rounded up to the nearest whole number.

Use the following formula to calculate the capacity of the snapshot data that you can store in the DP pool:

Capacity of the snapshot data that you can store in the pool = 
Total capacity of pool-VOLs in the pool - (Capacity of pool VOLs used by DP-VOLs + 
Capacity of V-VOL management areas)

Use the following formula to calculate the pool capacity:

Capacity of the pool [MB] = 
Total number of pages * 42 - 4200

Use the following formula to calculate the total number of pages:

Total number of pages = 
Sigma (floor (floor (pool-VOL number of blocks / 512) / 168)) for each pool-VOL

floor( ): Truncates the value calculated from the formula in parentheses after the decimal point.

Estimate pool-VOL capacity in multiples of 42 MB. Specifying a pool-VOL capacity in other multiples less than 42 MB truncates the fraction.