Backup Vault Size Calculator

Huawei Cloud CBR • Automatic

Disk capacity (GB) — a

Use the server capacity, not the used capacity. Tip

Backup retention period (days) — b

Don’t know the days? If you retain N backups and run K backups/day, then days ≈ N ÷ K.

Computed days from N, K: —

Daily changed data — c

Daily changed data (GB)

Include deleted, added, and changed data.

Formula result

— GB

— TB

Exact (no rounding). You can round up for safety based on your needs.

Walk-through

Vault = (a + b × c) × 200% = —

Where: a = disk capacity (GB), b = retention days, c = daily changed data (GB).

Quick rule of thumb (also from the docs)

2 × a = —

If you just want a quick estimate for automatic backups, set the vault to twice your total disk capacity.

How this works (formula explained)

Huawei Cloud recommends for automatic backup either:

Rule of thumb: set the vault capacity to twice the total capacity you want to protect; or
Precise estimate: use Vault (GB) = (a + b × c) × 200%

Here, a is the disk/server capacity in GB (not the used space), b is how many days you retain backups, and c is the total amount of data that changes each day in GB (counting additions, deletions, and modifications). Multiplying by 200% is equivalent to doubling the sum — it provides headroom for multiple backup versions and changed data over the retention window.

Source: Huawei Cloud “How Large of a Vault Do I Need?” (updated Aug 5, 2025). See the official doc for full context.
Open documentation

Manual backup scenario (no schedules): set the vault to the total capacity you want to back up.