Storage Growth
Enter used and total capacity and the growth rate (TB/month or %/month) and I compute when you hit the alert threshold and 100%, with the month-by-month projection.
Current occupancy
Month-by-month projection
| Month | Used | Occupancy | State |
|---|
How it is computed · linear vs. compound
Linear. Usage grows a fixed amount of
TB each month. Months to a target:
months = (target − used) / rate.
Compound. Usage grows a percentage
r over the previous level:
used × (1 + r)ⁿ = target, so
n = ln(target / used) / ln(1 + r).
Threshold. The threshold target is
target = total × threshold / 100. 100% is simply the
total.
Projection. Capacity at N months:
linear used + rate × N; compound
used × (1 + r)ᴺ.
! This is an estimate that assumes a steady rate. Real growth varies with retention, compression, deduplication and project spikes. Plan the expansion before hitting the threshold, not at 100%.
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How it works
The calculator projects when a storage pool will fill up from the capacity used today, the total capacity and the growth rate, with two models: linear (usage grows a fixed amount of TB each month) and compound (it grows a percentage over the previous month's level, like compound interest). It returns the months until the alert threshold you define (50–99 %, typically 80–90 %), the months until 100 %, the 6 and 12 month projections and a month-by-month table with approximate dates.
The formulas are direct. Linear: months = (target − used) / rate. Compound: from used × (1 + r)^n = target you solve n = ln(target / used) / ln(1 + r). The threshold target is total × threshold / 100. It is an estimate that assumes a stable rate: real growth varies with retention, compression, deduplication and project spikes.
Example: a 100 TB pool with 40 TB used, growing 5 TB/month
- Alert threshold at 80 %: target
100 × 0.8 = 80 TB; months(80 − 40) / 5 = 8 months. - Until 100 %:
(100 − 40) / 5 = 12 months, when the linear projection reaches40 + 5 × 12 = 100 TB. - With the compound model at 10 %/month the same pool hits 80 % sooner:
n = ln(80/40) / ln(1.1) ≈ 7.3 months, because each month grows on a larger base.