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Mac and Windows report HUGE free space difference on USB DAS?

Sal Sorice
Sal Sorice asked
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Last Modified: 2018-05-06
Stepping in to help a new client that lost their IT person in a tragic car accident. Sad.

That being said, I'm faced with multiple issues. One that is weird (and Mac related I think - not my forte) :

They have a Drobo device (Direct Attached Storage (DAS) via USB). It has (4) 1TB drives running RAID 1 (I think - not sure how Drobo works) - about 2.5TB of usable space. The Drobo reports that it is almost full.
However, a Mac user on the network says that they have tons of space free (14.92 of 17.57TB??)

We both see the same shared folder - any idea why there is such a HUGE difference in what we see?
I did a quick look at the Drobo and did not see anything like thin provisioning, etc.
Just trying to get my head around their entire network, etc. so I don't have much to go on or to offer. Just hoping a Mac person could shed some light on what they think they see as so much disk space - and what I see - almost out of space!
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bbaoIT Consultant
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Commented:
how about used space? a simple calculation of total and used space can tell you the real number of free space. then you can know which app gives the correct result, and then we can discuss why.
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Sal SoricePresident

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Thanks all for the comments. It does indeed seem like the Mac Finder is totally wrong. Just not sure why (or how) it could think there is 17.57TB of space on a device with only (4) 1TB disks! I could not find any evidence of thin provisioning, etc. that could account for the huge discrepancy. I'm gong to have the client run the Drobo Dashboard app and try the Mac commands mentioned to verify.
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It's not exactly wrong.  It's summing up the files it finds in each folder, including the deduplicated files.  This is actually the correct behavior.  The finder does not know that each file has a hard link to the same data.  You need to do a Get Info on the actual disk, instead of the mounted folder partition to get the Disk usage, rather than the folder usage.

The Windows system is showing the disk to be the Public folder, so it's showing the disk usage versus the folder usages.
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