Three Benefits of Windows 8 Storage Spaces | CIO.  (No longer available online. Original text included below.)

Small and medium sized businesses often can’t afford file servers, and struggle with the best way to provide their users with enough space to store data, while ensuring it is safe from hardware failure. Windows 8 will offer a feature called Storage Spaces has three benefits: bringing the safety of RAID to the desktop, creating an expanding space to store files, and providing these features at lower cost than currently available hardware solutions.

The Problem

How much disk space do you need, and how reliable is it? No matter how much disk space you buy, odds are you’ll fill it. Disk space is cheap, and USB drives are easy. This generally results in an assortment of variously sized USB drives attached to your computer, requiring numerous drive letters you need to spread your data across. If you want disk space that is protected against hardware failure, mirroring two disks requires they be identically sized or else you loose the extra capacity of the larger disk. For a level 5 RAID, that stripes data across more than two disks, you loose the capacity of each disk larger than the smallest in the RAID.

Expandable Space

To avoid the hassle of having multiple drive letters to store your data on, Storage Spaces allow you to create a virtual drive that you can expand when needed. It behaves much like a virtual machine, where you can create a disk that pretends to be 100GB in size, but initially may take up only 10GB of real space on your hard drive. As you add data to the virtual disk, the size of the real file grows as needed. Using thin provisioning, which gives the appearance of more space than actually exists, Storage Spaces can do the same thing, allowing you to create a storage pool in which multiple Spaces can exist that use the space they need, as they need it. If the Space you created fills the maximum size you initially set, you can even reset it to a larger size, resulting in the equivalent of a bottomless disk.

Protected Space

Making a bunch of disks look like one is handy, but could be dangerous if one of them should fail. Storage Spaces incorporates RAID technology to provide protection, ensuring at least one copy of all your data is available, even in the event of a hardware failure. It should be noted that Windows 8 isn’t the first to offer software RAID, Windows 7, XP and even 2000 included this capability. The difference is that the older versions required a static, predefined assignment of disks, where Storage Spaces allows you to dynamically add disks of varying sizes to grow the storage pool while still retaining redundancy of your data.

Cheaper Space

What Storage Spaces offers isn’t new, Data Robotics provides a hardware RAID system called Drobo that offers the same benefits, and other vendors have similar offerings. Unfortunately hardware solutions can costs hundreds of dollars for the base device, require specific types of disks, and are limited to the number of slots in the device. Windows 8 Storage Spaces requires no extra hardware, you connect any internal or external disks that you have and it uses them. This gives a business the flexibility to add space as needed, with an ever expanding virtual disk that is protected from hardware failure, keeping its data safe.