You can read all the details about this upcoming storage pooling technology, which will be available on both the Windows 8 client and server, versions:
"Virtualizing storage for scale, resiliency, and efficiency" by Steven Sinofsky 5 Jan 2012 11:15 AM
As the article explains, "A preliminary version of Storage Spaces is available in the Windows 8 Developer Preview," which is already available, but there is no GUI for it yet, only PowerShell commands.
Then this week, this new, complementary article:
"Building the next generation file system for Windows: ReFS" by Steven Sinofsky 16 Jan 2012 2:00 PM
with this fair bit of warning:
Being the first version of a major file system, we do suggest just a bit of caution. We do not characterize ReFS in Windows 8 as a “beta” feature. It will be a production-ready release when Windows 8 comes out of beta, with the caveat that nothing is more important than the reliability of data. So, unlike any other aspect of a system, this is one where a conservative approach to initial deployment and testing is mandatory.
So, could this mean? Start with the easier to interpret arstechnica article on ReFS (Resilient File System).
But as far as what could this all mean to the home server & backup enthusiast? Have a listen to David McCabe's comments, on the recent Home Server Show 169, at 35 minutes in. He indicates that Storage Spaces does seem to be the future Windows Drive Extender. That's the capability that Windows Home Server used to have, to join multiple drives together as one seamless drive letter, only to be strangely taken away in the latest version, Windows Home Server 2011. Seems less strange now, doesn't it?
Also note that the new thin provisioning capability in Storage Spaces is an old concept for VMware ESXi users, given the VMware VMFS filesystem that has allowed VMs to be thin provisioned for years.
Just a hunch, but I would guess you'd want to thick provision a VM on the VMFS filesystem, if you wish to thin provision ReFS Storage Spaces inside that VM, for performance reasons. Or perhaps just use ReFS without any thin provisioning, and instead thin provision the VM on the VMFS filesystem, for probably even better performance. Time and testing will tell.
But that's well into the future, and Storage Spaces/ReFS aren't even available for boot drives, and ReFS is Windows-Server-only, for now.
Let's all hope for a Duncan Epping masterpiece on this whole matter, on yellow-bricks.com, someday...