total capacity
Computing term for the combined storage or data capacity of a system, drive, or set of components.
The total capacity of this server is 10 terabytes.
Calculate the total capacity of multiple hard disks.
容量 means capacity in general; 合計容量 specifically refers to the total combined capacity.
合計 means total or sum; 合計容量 is the total capacity, a compound noun.
Compound of 合計 (total) + 容量 (capacity).