Q: shared storage shows different values -- why?

Dec 19, 2012
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Hi.
I just installed a 2-node-cluster on Proxmox 4.1.
When I add a storage in my datacenter I can enable
[x ] Shared.

Now this storage is shown on all nodes -- but it shows different available GB of storage on each node.
Why?

On node 1: 737 GB Avail - Used 898 GB but on
node 2: 85 GB Avail - Used 4 GB
It doesn't happen with NFS-Shares on both nodes.
So: What's the problem here?
Thanks.