Backup Storage & Retention
Storage a full + incremental backup schedule needs for a retention window, from data size, daily change, full interval and your compression ratio, plus growth.
The backup capacity now and after growth, what is written each week, and the number and size of fulls and incrementals kept — every rate yours, none assumed.
Example: 2 TB changing 2 % a day, a full each week kept 30 days: 5 fulls + 25 incrementals = 11 TB raw, 5.5 TB at 2:1; 6.6 TB after a year of 20 % growth.
Fulls kept,
plus incrementals.
The simple schedule the page models, how retention turns into copies, why the compression ratio is yours, and which real-world schemes need translating into these terms.
The schedule
A full backup every N days with an incremental (only the day’s changes) on the other days, everything kept for the retention window. Fulls kept = ⌈retention ÷ N⌉ — a partial cycle rounds up to a whole full, because the oldest incrementals need their full to restore. Incrementals kept = retention − fulls. Storage = fulls × data + incrementals × data × daily change, divided by the compression ratio.
Rates are inputs
Daily change and compression depend entirely on the data: databases and mailboxes churn, archives do not; text and logs compress several times over, video and already-compressed files barely at all. The page assumes a ratio of 1 (none) and a change rate you enter; take both from what your backup software reports on the current job.
Other schemes
Forever-incremental with synthetic fulls stores roughly one full plus the retention’s incrementals — set the full interval to the retention length. Deduplication across fulls behaves like a higher ratio. Grandfather-father-son tiers (daily, weekly, monthly) are the sum of several of these schedules; run the page once per tier.
What the number does not settle
Growth is applied uniformly as a compound yearly rate over the horizon you set. Restore time, bandwidth to an off-site copy (the weekly figure is the ingest to plan for), verification copies and the 3-2-1 rule’s extra copies are not included. RAID Capacity sizes the target array. Inputs stay in your browser; the same four anonymous usage counts as the rest of the site apply.