I have been looking around for a guide for forecasting growth of storage for budgeting purposes. We currently have 160Gb (60Gb Tier 1, 100Gb Tier2). So I am trying to estimate how much is likely to be required in 1,2,3,4,5 years time.

CAGR (Compounded Annual Growth) is apparently the figure to use but whitepapers I have read give a CAGR of anywhere between 15-60% and no explanation of how this number is arrived at is ever given.

Is there a rough industry standard/guideline that anyone is aware of? Doesn't have to be exact, just from a respected source so it can be used in the forecast and quoted.

cheers