Storage Spaces in Windows

You need at least two extra drives (in addition to the drive where Windows is installed). These drives can be internal or external hard drives, or solid state drives. You can use a variety of types of drives with Storage Spaces, including USB, SATA, and SAS drives.

External USB drives can work normally in File Explorer but still not appear in Windows Storage Spaces. Storage Spaces only accepts disks that Windows recognizes as eligible physical disks, not just usable storage. Many USB enclosures and hubs add an abstraction layer that causes Windows to treat drives as removable or to hide multiple disks behind a single device identity, which Storage Spaces excludes by design. This behavior is expected and not a Windows bug. 

Common causes include USB enclosures that report drives as removable, RAID‑capable or “smart” enclosures that hide individual disks, and USB hubs that collapse multiple drives into one device path. Reinstalling Windows, updating drivers, or changing power settings does not change disk eligibility when the limitation comes from the hardware.

Users can check eligibility by selecting the disk itself (not the volume) in Device Manager or Disk Management and confirming whether Windows reports it as Fixed or Removable. USB drives depend on enclosure firmware. SATA drives that connect directly are usually eligible, as are enterprise‑grade SAS drives.

1. Add or connect the drives that you want to group together with Storage Spaces.

2. Go to the taskbar, type Storage Spaces in the search box, and select Storage Spaces from the list of search results.

3. Under Add a new Storage Pool, select Add. 

4. Give pool a name, choose drives to use under Add disks and select Create.

5. Type a name for the new Storage Space.

6. Choose a resiliency, Simple (no resiliency). Two-way mirror (default), Three-way mirror, Parity, or Dual-parity to help protect the files in the storage space from drive failure. Resiliency is the ability of storage spaces to create copies of data across multiple drives. 

7. Enter the maximum size the storage space can reach, and select Create.

8. Type a name for the volume Label on the new drive, and assign it a Drive Letter. 

9. Select the File System dropdown and choose a file system to use.

10. Select Format. 

• Simple spaces are designed for increased performance, but don't protect your files from drive failure. They're best for temporary data (such as video rendering files), image editor scratch files, and intermediary compiler object files. Simple spaces require at least two drives to be useful.

• Mirror spaces are designed for increased performance and protect your files from drive failure by keeping multiple copies. Two-way mirror spaces make two copies of your files and can tolerate one drive failure, while three-way mirror spaces can tolerate two drive failures. Mirror spaces are good for storing a broad range of data, from a general-purpose file share to a VHD library. When a mirror space is formatted with the Resilient File System (ReFS), Windows will automatically maintain your data integrity, which makes your files even more resilient to drive failure. Two-way mirror spaces require at least two drives, and three-way mirror spaces require at least five.

• Parity spaces are designed for storage efficiency and protect your files from drive failure by keeping multiple copies. Parity spaces are best for archival data and streaming media, like music and videos. This storage layout requires at least three drives to protect you from a single drive failure and at least seven drives to protect you from two drive failures.

After you upgrade to Windows, we recommend that you upgrade your existing pools. With an upgraded pool, you can optimize drive usage and remove drives from pools without affecting the pool's protection from drive failure.

When you add new drives to an existing pool, it's a good idea to optimize drive usage. This will move some of your data to the newly added drive to make the best use of the pool's capacity. It'll happen by default when you add a new drive to an upgraded pool in Windows you'll see a check box for Optimize to spread existing data across all drives selected when you add the drive. However, if you cleared that check box or added drives before upgrading a pool, you'll need to manually optimize drive usage. To do so, type Storage Spaces in the search box on the taskbar, select Storage Spaces from the list of search results, and then select Optimize drive usage.

If you created a pool in Windows or upgraded an existing pool, you'll be able to remove a drive from it. The data stored on that drive will be moved to other drives in the pool, and you'll be free to use the drive for something else.

1. Press the Windows key, type Storage Spaces and select Manage Storage Spaces from the list of search results.

2. In the Manage Storage Spaces dialog, select Physical drives to see all the drives in your pool.

3. Find the drive you want to remove and choose Prepare for removal and select the Prepare for removal button. Leave your PC plugged in until the drive is ready to be removed. Files on the removed drive are copied to another drive in the pool. This could take several hours, depending on how much data you have stored there.

   Tip: To speed up drive preparation, prevent your PC from going to sleep.
   Press Windows key + I, select System and choose Power & battery. Under Plugged in, select the dropdown next to Make my device sleep after and choose Never.

4. When the drive is listed as Ready to remove, select Remove and choose Remove drive. Now, you can disconnect the drive from your PC.