Any server
Backup Storage Plan
Backup retention is chosen in days and billed in gigabytes, and turning one into the other catches people out. Fourteen daily copies of a world that keeps growing come to more than fourteen times today's size, because the world gets bigger while the policy runs.
Backup Storage Plan
The real storage cost of a retention policy — usually higher than people plan for.
Storage needed
14 full copies
Size of the newest copy
World size after 14 days
Uncompressed, on the server
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How the numbers are worked out
Full copies are the easy case and the costly one: each backup holds the entire world, and because the world grows over the retention window, the typical copy sits halfway between today's size and the size on the last day. Multiply that by the number of copies kept. Incremental works differently — one complete copy plus the daily changes on top — and for a world that grows slowly it comes out far smaller. Compression is applied at the end as a flat percentage off the total.
The formula
- size after N days = current + growth × N
- average full copy = (current + size after N days) ÷ 2
- full total = average copy × copies × (1 − compression)
- incremental total = (size after N days + growth × N) × (1 − compression)
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Common mistakes
Daily growth drives the result more than anything, and it is the value people guess. Measure it instead by checking the size of the world folder two days running. The other trap is how often you back up: four copies a day instead of one does not cost a bit more, it costs four times as much, since every copy is a full one unless you have deliberately set up incremental.