Capacity
Estimate storage growth before choosing drive size
The first useful number is the protected capacity target for the planning horizon—not the sum of drive labels in a cart.
Decision 01
Start with data classes
Separate irreplaceable photos and documents from replaceable media, caches, downloads, and operating-system images. They need different recovery targets and may grow at different rates.
Decision 02
Use a visible horizon
Choose a one-, three-, or five-year horizon and record the monthly growth assumption. A range is more useful than a false precise forecast.
Decision 03
Leave operational headroom
Snapshots, metadata, temporary copies, and maintenance all consume room. Keep the reserve visible instead of filling a pool to its headline capacity.