Storage Spaces

Storage Spaces works only with Intel x86/x64 versions of Windows 8, not with ARM‑based Windows RT systems.

NTFS and other filesystems have their advantages, but the reliability of any filesystem is ultimately tied to the weakest link in the chain, the underlying storage hardware. It’s a simple fact of life that hard drives (and related storage devices) fail, and that when they do so, they often bring your data down with them.

Windows has used various technologies over the years to help overcome the inevitability of data loss. For example, Windows 7 includes a feature called Previous Versions that automatically stores document revisions so that you can later go back and resuscitate an older document version when needed. It also includes a Windows Backup utility that does a decent job of backing up important files, or even the entire PC.

These and other recovery solutions are reactive, meaning they provide help in the event of a worst‑case scenario, be it the accidental deletion of a file, the overwriting of a file with an older, less correct version, or whatever. But they don’t solve the underlying problem of relying on a single hard disk (or other device). They don’t, for example, replicate your critical data across two or more disks automatically so that if one drive fails, your data is still safe.

Storage Spaces is conceptually related to a technology called Drive Extender, which debuted in a product called Windows Home Server. That said, Storage Spaces is the superior solution and is technically unrelated to Drive Extender.

Windows 8 includes such a feature. It’s called Storage Spaces, and it works with both NTFS‑ and ReFS‑formatted disks, providing a safe, secure, and redundant way for you to provision, manage, and use storage that spans multiple disks, replicating your data automatically.

Storage Spaces provides two basic services:

• Data redundancy : Storage Spaces utilizes data mirroring technology to ensure that there are at least two copies of data, each of which lives on a different disk, to help prevent data loss in the event of a hard disk failure. Storage Spaces lets you configure up to three disks for redundancy purposes. (It also supports a parity feature, which provides you with two different copies of your data but requires three physical disks; the third disk is used for parity purposes.)

• Single pool of storage : You can organize the storage on your various hard disks in one or more storage pools that are managed as a single entity–called a storage pool , or simply pool –despite having storage that could span many disks. And unlike complex technologies such as RAID, these disks can be of multiple different sizes and types, and can include fixed disks (SATA) and external storage (like USB). You’re free to mix and match as you like, and adding storage to a storage pool is as simple as plugging in a new disk and adding it to that pool using a very simple interface.

Storage Spaces is easy to set up and configure, and once you do that, you can pretty much just get on with life and not worry about it anymore. Storage Spaces also integrates with File Explorer, much like libraries do. This means you get a normal view of the storage from Explorer, and it uses a normal, widely understood drive letter, appearing to look and work just like a simple hard drive. This is useful for users, but also for the OS and any applications, since they’ll expect such things. This means the compatibility of Storage Spaces is excellent.

Storage Spaces also lets you create a space that is bigger than the total amount of physical storage. This feature, which is called thin provisioning , lets you preconfigure a space to a large size and then add physical storage later, when it’s actually needed. Likewise, physical storage is only allocated as it’s needed. (You’ll be prompted when needed through Action Center, which uses a Windows Troubleshooting notification.)

Finally, in addition to working with normal NTFS‑based disks, Storage Spaces is also compatible with ReFS‑based disks. This means that today on Windows Server 2012, you can optionally mix and match NTFS and Resilient File System (ReFS)‑based disks. And in the future, you’ll be able to do so on Windows as well.

As is always the case with new technology, Storage Spaces brings with it some new terminology. Where a storage pool can consist of the storage on one or more disks–though of course you’d need two or more for redundancy–you access this storage via a new entity called a storage space , or space . To understand what this means, consider how libraries work in Windows 7 and 8. In these operating systems, you have physical folders such as My Pictures and Public Pictures, and the combined, virtual view of these folders is called the Pictures library. Spaces work the same way. You may combine your E: and F: drives into a single pool of storage. But you will access that pool through the filesystem using a virtual view called a space, and that space will be given a name. In this case, it could be called the Pictures space.

So storage spaces have names and drive letters. But they also have an assigned resiliency type. This determines how (or whether) the data stored in the space is synced automatically across two or more disks, or what is called redundancy. The available resiliency types include:

• None : In this configuration, the space works exactly like a normal hard drive. Data is not mirrored on two or more disks but is instead stored on just a single disk. This configuration requires a storage pool with at least one physical disk.

• Two‑way mirror : Here, your data is mirrored on two physical hard disks, protecting that data from a single hard disk failure. This configuration requires a storage pool with at least two physical disks. However, the available storage in the pool will be halved, assuming both disks are the same size.

• Three‑way mirror : In this configuration, your data is mirrored on three physical hard disks, protecting that data from the failure of two hard disks. This configuration requires a storage pool with three physical disks. However, the available storage in the pool will be one‑third the total, assuming all three disks are the same size.

A parity configuration is notably good for storing very large files, like videos.

• Parity : In this advanced configuration, your data is mirrored alongside additional parity information that could help Windows recover data in the event of a hard drive failure.

Because spaces have this unique capability to reserve more storage than is physically available in the attached disk(s), the feature lets you plan for the future by pretending that you have more storage than you do. If the data stored in the space begins exceeding your physical capacity, you’ll be notified to add more physical storage.

Meanwhile, because Storage Spaces uses thin provisioning to allocate only a small amount of physical storage when a new space is created, even if you create a space of multiple terabytes, only 1 GB of space is actually taken right away.