Microsoft Touts Windows 8's Storage Virtualization
Microsoft says Windows 8's new "storage spaces" feature will work with the updated operating system's New Technology File System (NTFS).
The storage virtualization feature in Windows 8 can aggregate groups of hard drives and solid state drives into a storage pool, which virtualizes the disks. Users can then create "Spaces" from these pools with a logical capacity of up to 10 TB, although the maximum size can be increased.
It's possible to create a 10 TB space using just two 2 TB disks using Microsoft's thin provisioning feature in Windows 8. According to a Windows 8 blog post by Rajeev Nagar, a group program manager on Microsoft's storage and file system team, "thin provisioning ensures that actual capacity is reserved for the space only when you decide to use it." As files are deleted, capacity is automatically reclaimed, he said.
Many automated processes are enabled using storage spaces, such as automatic file duplication and disk failover protections. There is a built-in mirroring capability to protect data against disk failures, and users can swap out disks as needed and the system is self-healing.
A "parity" attribute provides additional support in case of disk failure. This parity feature allows users to reconstruct files after a failure. Microsoft suggests that parity might be best used to protect large files that don't change too much, such as multimedia files. For smaller files that change frequently, such as document files, mirroring capability represents the best protection.
The ability to use lower-cost disks, such as "just a bunch of disks" (JBODs), is a Windows 8 feature with storage spaces, echoing the storage improvements found in Windows Server 8. Windows 8's storage spaces feature will let users pool mixed devices, such as USB drives and serial ATA (SATA) devices with different capacities, according Nagar's post. He noted that "we do not recommend iSCSI drives in a Storage Pool except for test deployments." That, at least, is a contrast with Windows Server 8, which supports iSCSI.
The real comparison for storage spaces is not with Windows Server 8 but with a deprecated feature in Windows Home Server called "drive extender." Microsoft removed drive extender from Windows Home Server 2011 (formerly code-named "Vail"), which caused a furor among Windows Home Server users. Drive extender had allowed Windows Home Server users to pool multiple hard drives without resorting to a redundant array of independent disks (RAID) approach. Now, Microsoft has brought drive extender's capabilities back.
"Storage Spaces is not intended to be a feature-by-feature replacement for that specialized solution [drive extender], but it does deliver on many of its core requirements," Nagar stated in the blog. "It is also a fundamental enhancement to the Windows storage platform, which starts with NTFS. Storage Spaces delivers on diverse requirements that can span deployments ranging from a single PC in the home, up to a very large-scale enterprise datacenter."
The "We Got Served" blog, which has tracked the drive extender controversy among users, commented that storage spaces technology seems to be more complex than drive extender. The addition of storage spaces to Windows 8 might even represent a death blow to Windows Home Server's future, according to Terry Walsh, founder of the "We Got Served" blog.
"In today’s blog post, Microsoft are dropping heavy hints that they consider Windows 8 Client to be the natural successor to Windows Home Server -- via nods from both Steven Sinofsky and Nagar as to the Storage Spaces' provenance as well as a FAQ regarding migration from WHS v1 to Windows 8," Walsh stated.
Microsoft indicated in its FAQ that Windows Home Server users of drive extender would have to first set up storage spaces on Windows 8 and then copy the data over. The two systems will not work together. Additionally, the Windows 8 storage spaces feature is not backward compatible with Windows 7.
As with Windows Server 8, PowerShell is the key tool for customizing and automating in Windows 8, although a GUI can be used to set up storage spaces, too. IT pros should consider using PowerShell with storage spaces for "more advanced tasks," according to Nagar.
Storage spaces is available now in the Windows 8 developer preview for testing, but Nagar cautioned that some advanced PowerShell commands might not work. For that to happen, users will have to wait for the Windows 8 beta, which is expected to be available in late February. Currently, the space size in the developer preview is just limited to 2 TB using storage spaces, but that restriction will be removed in the beta. According to the Q&A accompanying Microsoft's blog post, there will be "no architectural limit to the number of disks comprising a pool" using the storage spaces feature.
There's also no CHKDSK utility for storage spaces. Corrupt disks can just be swapped out, according to Microsoft's blog. Users will be able to spot bad disks using PowerShell commands.