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[John Dickinson <me@xxxxxx>]

On Feb 11, 2012, at 7:29 AM, Jorge Luiz Corrêa wrote:
> 
> 2) About Swift, how do I determine the total usable storage capacity of the system? For example: I have 3 nodes with 5 HDs of 1 TB each one. Straightly I have 15 TB of space. If I use raid 1 I can say that I'm going to have 7,5 TB of usable space. And with Swift, is it possible to determine this usable space? 

Here's how to find the usable space for swift

marketing size of the drive (eg 2TB) * .92 (to account for formatted size * .8 (for 80% fullness) / replicas

If you have 15 TB of formatted space with 3 replicas, that gives you 5TB of usable space. If you have 15TB of unformatted space with three replicas, that gives you a little less than 4TB of usable space.

The reason I calculate it at 80% fullness is so that you have some headroom to expand as your cluster grows. You don't want to have your hard drives fill up completely before you decide it's time to buy some new ones.

--John

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