It seems like a stupid question, if you’re not an IT professional – and maybe even if you are – how much storage does it take to store 1TB of data? Unfortunately, it’s not a stupid question in the vein of “what weighs more, a pound of feathers or a pound of bricks”, and the answer isn’t “one terabyte” either. I’m going to try to break down all the various things that make the answer harder – and unhappier – in easy steps. Not everybody will need all of these things, so I’ll try to lay it out in a reasonably likely order from “affects everybody” to “only affects mission-critical business data with real RTO and RPO defined”. //

TL;DR: If you have 280GiB of existing data, you need 1TB of local capacity. //

8:1 rule of thumb
Based on the same calculations and with a healthy dose of rounding, we come up with another really handy, useful, memorable rule of thumb: when buying, you need eight times as much raw storage in production as the amount of data you have now.

So if you’ve got 1TiB of data, buy servers with 8TB of disks – whether it’s two 4TB disks in a single mirror, or four 2TB disks in two mirrors, or whatever, your rule of thumb is 8:1. Per system, so if you maintain hotspare and DR systems, you’ll need to do that twice more – but it’s still 8:1 in raw storage per machine.