Storage Spaces provide some level of fault tolerance (resiliency). If one disk in the pool fails no data is lost and a failed disk can be easily replaced. To a certain extent this function is identical to RAID (redundant array of independent disks) Level 1 (“mirror”) and Level 5 (striping with distributed parity). But unlike RAID Storage Spaces allow us to combine disks of any type and size. However, if you are already using a hardware or software RAID, then switching to Storage Spaces makes no sense since you will not get any benefits (data protection or performance).
Storage Spaces can be used to store of files' history and system image backups, temporary (configured as simple) or really important files (configured as 2-way mirror or parity). The function works with NTFS-formatted drives and allows you to set special permissions for files and folders or enable content encryption (BitLocker is also supported). Windows 8/8.1/10 recognizes relatively new ReFS file system so this format can also be selected when creating Storage Spaces.
Unlike traditional drives Storage Spaces do not need to be defragmented. There is also no need to use disk check on them. In case of any problems Windows immediately notify you. If one of the physical disks becomes damaged just disconnect it, restore and add it to the pool again.
If you combine disks with similar performance (two identical internal hard drives) the overall speed of reading speed increases significantly. While the write speed slightly drops. When combining internal and external disks the read & write speeds are slightly higher than the slowest disk in the storage pool.
Although Windows 8, 8.1 and 10 allow you to mix disks of different sizes it is recommended to use disks of the same size to avoid of disk space waste. For instance, by connecting one 300 Gb disk and one 750 Gb disk in a double-sided mirror you get 525 Gb disk space (virtual disk). The calculation is the following: (300 + 750) / 2 - to ensure resiliency only half of the total disk space is available when using a 2-way mirror. The remaining space is used for data backup. But since mirroring implies that all disks in the storage pool contain the same data the actual usable space is limited to 300 Gb (the smallest physical disk in the pool simply cannot store more data). This means that an additional 450 Gb on a 750 Gb disk is not used and we are not able to store more than 300 Gb unless you add the disk(s) with a capacity that is sufficient to provide resiliency in case of failure of the largest disk. Of course you can remove small disks and replace them with more capacious ones later - but only one at a time to avoid data loss.
Storage Spaces can be easily connected (in any order) to any other computer with Windows 8/8.1/10 but earlier versions of Windows do not support Storage Spaces - for them, as we said, this is an unrecognized partition.
And finally it is important to note that the system disk (on which the operating system is installed) cannot be added to Storage Spaces logic.