Storage Spaces in Windows 8, 8.1, and 10 allow combining multiple hard disk drives (HDD) or solid-state drives (SSD) into one storage pool. The drives can be connected to any interface (ATA, SATA, SAS, or USB) and you can combine disks that are different in size. A Storage Space is actually a virtual disk and it is usable in Windows just like any other drive.
The main reason for Storage Spaces is to provide some form of fault tolerance - if one drive in a storage pool fails, you will not lose your data and you can easily replace the failed disk later. In many ways, the feature is identical to RAID (Redundant Array of Inexpensive/Independent Disks) levels 1 (mirroring) and 5 (striping with distributed parity), but unlike in RAID, you can combine disks of any type and size into Windows 8/8.1 and 10 storage pools.
If you are already using hardware or software-based RAID, you should not use these drives with Storage Spaces, because there are no gains in data protection or performance.
There are special drive enclosures on sale that conform with Windows 8, 8.1, and 10 Storage Spaces requirements - these ones can even light up notification LED-s for failed drives.
A Storage Space in Windows 8 and newer is always NTFS-formatted and you can set file and folder security or enable Encrypting File System (BitLocker is also supported). Windows 8/8.1/10 also recognize the new ReFS format used in Windows Server 2012.
Unlike for traditional drives, there is no need to defragment Storage Spaces, or use Check Disk on them. If files on a member drive do get messed up (Windows will notify of this immediately), just disconnect and reconnect it.
If you combine drives that have similar performance characteristics (for example, two identical internal hard drives), the overall file reading speed will increase noticeably, while writing speed will decrease a little.
In case you combine internal and external drives, read and write performance will be a bit higher than that of the slowest drive in Storage Pool.
Although Storage Spaces in Windows 8, 8.1, and 10 allow mixing drives of different sizes, it is recommended to use drives that have a similar capacity to avoid wasting disk space. For example, if you put one 300 GB disk and one 750 GB disk into a two-way mirror, you'll get a Storage Space (virtual disk) of 525 GB in size. The calculation is (300+750)/2 - to provide fault tolerance, only half of the total disk space is available while using the two-way mirror. The other half is used for data redundancy in case one of the drives goes offline for some reason.
But mirroring means that all member drives contain exactly the same data. That's why the real usable space in this example maxes out at 300 GB (the smaller physical disk just cannot hold more data). This means that the extra 450 GB of disk space on the 750 GB drive will not be used and you will not be able to store more than 300 GB of data unless you add drive(s) that provide enough capacity for fault tolerance in case the larger drive dies.
Of course, you can remove smaller drives and replace them with larger ones later - but only one at a time to avoid data loss.
As usual, there is a larger catch - you cannot add your system drive (the one where Windows is installed) to a Storage Space, and you cannot boot your PC from a Storage Space.
And while you can connect your Storage Space drives (in any order) to any other Windows 8/8.1/10 computer without problems, older Windows version will not recognize the drives and Storage Spaces - for them, this is an unrecognized partition.
To create a new Storage Space, you must have at least two physical hard drives (your Windows drive does not count here!) or Solid State Drives (SSD-s). You cannot use USB sticks/flash drives or memory cards for Storage Spaces.
The drives can be formatted or unformatted. For the latter, prior initialization via Disk Management is not required. During the Storage Pool creation process, the selected drives will be formatted, so please do back up all important data on them before taking any further steps! See, I warned you.
In Windows 10 May 2020 Update (version 2004), partition for Storage Spaces might show as RAW in Disk Manager. Do not run chkdsk on such partition until Microsoft resolves this problem! If you do, you risk losing all data on that partition! Microsoft has blocked upgrading Windows 10 to version 2004 on such systems.
It is best to disconnect this Storage Space until the problem has been resolved, or you can use Microsoft's recommended solution of making the partition read-only.
In Windows 8 and 8.1, open Settings search using keyboard shortcut Windows Key+W, type "storage" into the Search box and click Storage Spaces.
Touchscreen users should first swipe in from the right edge of the screen and tap/touch Search.
In Windows 10, open the Start menu, type "storage" and click the correct result.
The Manage Storage Spaces window opens. Click Create a new pool and storage space.
User Account Control will kick in and verify that you really want to allow Storage Spaces Settings to make changes. Click Yes.
In the Select drives to create a storage pool window, both formatted and unformatted drives are displayed (except your system drive, of course). You must expand the Formatted drives section to see the available drives. Use checkboxes to select the ones you want for your new Storage Space.
Here's your last warning - all selected drives will be formatted during the creation of a Storage Space and you will lose any data on them (Recycle Bin does not help here)!
If there are no suitable drives available, the "No drives that work with Storage Spaces are available. Make sure that the drives you want to use are connected." message is displayed instead. Make sure you have connected hard disk drives or SSD-s, not USB flash disks or memory cards.
Click Create pool.
Next, Enter a name, resiliency type, and size for the storage space window opens.
In the Name and drive letter section, you can change the drive label (name) and drive letter if you want to.
In the Resiliency section, select how you protect your data:
- Two-way mirror - requires at least two drives and protects from a single drive failure. This is similar to RAID level 1 (mirroring) and it increases read performance. This is the most common option.
- Three-way mirror - requires at least five drives and protects from two simultaneous drive failures. This is similar to RAID level 10 and it increases both read performance and data protection.
- Parity - requires at least three drives and protects from a single drive failure. This is similar to RAID level 5 and its read performance is slower than on mirrored drives. This type is intended for large files that do not change often - videos, for example.
- Simple (no resiliency) - requires at least one drive and has no data protection. Multiple drives are used as one large drive, but if one disk fails, all data in the Storage Space will be lost. This is similar to RAID level 0 (striping) and it increases both read and write performance. You should create such drives for storing large temporary files only - no data protection is available in this case.
In the Size section, you can set the maximum size for the Storage Space. Windows sets the Size (maximum) field automatically according to the Resiliency type selected: two-way mirrors have half the space displayed in Total pool capacity line (the sum of disk space on all included drives); three-way mirrors have one third and parity has two-thirds of the value. This is because some disk space is used for backing up data on other member drives of the Storage Space.
Please note that you can set the Size (maximum) value much larger than the value displayed - if you run out of physical disk space on a Storage Space, just add and assign another drive. This is called Thin Provisioning.
Remember that decreasing Storage Space size later is not possible, but increasing is.
Finally, click Create storage space.
The process will take a little while and then the Storage Space will be available in Windows Explorer as any other hard drive.
By the way, one Storage Pool can contain several Storage Spaces if there is enough pool space available.
To change Storage Space name and capacity later, click Change in Manage Storage Spaces window, Storage spaces section. If the command is grayed out, click the Change settings button in the top right of the window first.
In the Enter a new name and size for the storage space window, you can change both the name and drive letter of the Storage Space.
In the New size section, you can only increase the Storage Space size. Decreasing the capacity is not possible in Windows 8, 8.1, or 10.
As you might have noticed, switching the Resiliency type (mirroring, simple, or parity) is also not possible.
Click Change storage space after you've done making changes.
You can also rename Storage Pools and physical drives in Storage Spaces. The appropriate commands are easy to find in the Manage Storage Spaces window.
If your Storage Space or Pool is running out of usable capacity, or if you want to expand it, connect the new drive(s) first.
Next, open the Manage Storage Spaces window from the Start screen/menu or Control Panel.
Click Add drives in the Storage pool section. You might have to click the Change settings button in the top right corner of the window to access the command.
Select the disk(s) you want to add to the storage pool from Unformatted drives or Formatted drives section and click Add drives.
Please remember that selected drive(s) will be formatted and all data on them will be lost! If there is something important on a formatted drive, copy or move it elsewhere first.
If your Storage Space had no free virtual disk space, you must change its maximum size now.
Removing drives from Storage Spaces in Windows 8, 8.1 and 10
To remove a failed, disconnected, or unneeded drive from a Storage Space, open the Manage Storage Spaces window from Control Panel or Start.
You can also remove a small drive to replace it with a larger one - but please do this only one drive at a time to avoid data loss.
First, click the Change settings button in the top right corner of the window to access available commands.
Then click Remove for the physical drive. Please note that not all drives can be removed - those essential to the health of the Storage Space do not have the Remove command.
In the Confirm removal of the drive window, click Remove drive.
In some cases, you might see the "Can't remove the drive from the pool. Drive could not be removed because not all data could be reallocated. Add an additional drive to this pool and reattempt this operation" error.
This means that remaining drives do not have sufficient free space to support the removal of the member drive.
Click Close and proceed as suggested.
In the case of a two-way mirror, the Remove button/link is not available. If you want to replace or upgrade drives in such Storage Space, shut down your device, disconnect the physical drive you want to remove from the Storage Pool, and connect the new drive. Then start your computer and open Storage Spaces configuration.
Do note that if the physical drives are of different sizes, you should replace the smaller drive first - otherwise you might experience data loss or even lose the whole Storage Pool/Space.
First, click or tap the Change settings button, then use the Add drives link in the Storage pool section and select your new drive. Shortly after adding a new drive, you can click Remove for the disconnected drive in the Physical drives section.
Please note that the "Cannot remove drive from the pool" warning might appear, but the old drive will still be removed from the pool after clicking OK.
You might want to remove a Storage Space if you need to change its Resiliency type, or if you do not need it at all. Please be aware that deleting a Storage Space erases all information on it - if there is something important on the Space, copy or move it elsewhere first.
Open the Manage Storage Spaces window using the Start screen/menu or Control Panel.
First, click the Change settings button in the top right corner of the window to access available commands.
Then click Delete for the Storage space you want to get rid of.
Click Delete storage space in the Confirm deletion of the storage space window.
After you've deleted all Storage Spaces, you can also remove Storage Pool. This will make all the drives included in the Pool visible to Windows 8 as individual disks.
Click Delete pool in the Confirm deletion of the storage pool window.
Windows Action Center lets you know if problems with Storage Spaces appear. Action Center (the white flag icon in Windows 8 and 8.1; speech box icon in Windows 10) is visible in the Notification Area of Taskbar (aka System Tray).
First, if 70% of Storage Space capacity is reached or a member drive goes offline, a "Check Storage Spaces for issues" notification appears in Action Center. Click it to see additional details.
Here's the example of low disk space - a small member drive is almost full. Storage pool status says "Low capacity; add drives" and Storage spaces status says "Warning. Low capacity; add 2 drives".
You can either delete unneeded files or add new drives.
A worse case is when a member drive is disconnected or has failed.
In such cases, Storage pool status reads "Drive issues; check the Physical drives section for Warnings or Errors" for missing drives and "Unhealthy drives; check drive health" for failed drives.
Storage spaces status reads "Warning. Reduced resiliency; check the Physical drives section" for missing drives and "Warning. Degraded; check drive health" for failed drives.
Expand the Physical drives section and find the drive with warning status. If the drive is missing or has failed, its status is "Warning. Disconnected; reconnect drive".
Either reconnect the missing drive or replace the failed one as soon as possible (add the replacement drive and then remove the failed one). Windows 8/8.1/10 will then rebuild the data on reconnected or new drive quickly (much faster than RAID systems do).
In case a member drive fills up 100%, the Storage Space will be taken offline. Action Center notification reads "Check Storage Spaces for problems (Important)" in such a case.
Click it to open Storage Spaces.
The Storage pool status is "Drive or storage space issues; check the Physical drives and Storage spaces sections" and Storage spaces status is "Error. No capacity; add 2 drives".
Either add drives to the Storage Pool to expand Storage Space maximum size or delete unneeded files and folders after clicking Bring online in the Storage spaces section.