17.5 TB Available?

I am playing with my new FS, and finder shows my public share as having 17.5 TB Available. I have (3) 2TB drives installed, and am running 10.6.5 on an iMac and 10.6.5 server on a mini server. drobo dashboard (1.7.30095) with drobo firmware (1.0.5(4.21.3025) shows 3.57TB Free Space (25.05 GB used).
I read somewhere that I had to format the drobo volume using disk utility. disk utility does not show the drobo.

This comes to mind: http://www.suitetake.com/2009/08/21/the-dark-side-of-drobo/

any help would be appreciated, Thanks

You “see” more storage than is physically available because of Thin Provisioning, which lets you increase the physical storage size without having to format/repartition.

Without Thin Provisioning, you’d end up with multiple volumes (you still can if you set the volume size smaller than your physical storage).

It’s a little less of an issue with network-attached storage (though the embedded OS still has to deal with the volume size), but it’s a pretty big deal for direct-attached storage. Resizing of volumes can be tricky and time-consuming.

Thanks for the quick response

To add to bhiga, Snow Leopard changed the way it reports volume sizes. A 16 TB volume will show up as 17.49. If you look at your Drobo FS from a Leopard machine it will show up as 16 TB.

Good point Kurt. Yup, Snow Leopard uses SI prefixes (1 kilobyte = 1,000 bytes) rather than the more-traditional-though-incorrect binary prefixes (1 kilobyte = 1024 bytes).

…and TiVo’s web interface used SI prefixes for as long as I can remember (at least Series 2 and onward, possibly), so TiVo wins on using SI prefixes (and unfortunately confusing geeks) first, at least in my world. I’m not aware of any other systems that have normalized to SI prefixes yet.

Wikipedia tebibyte (there’s a chart and links to the others)
SI units reference at NIST

aside from all the drive marketeers…

everyone should just move to SI and be done with it,

It’d be nice to be correct… not to mention consistent, heh.