When you create a mirror (raid 1) on an external disc enclosure, unplugging device, may cause raid configuration loss

Applies to: Windows 8.1Windows 8.1 EnterpriseWindows 8.1 Pro


When you are creating a mirror set (RAID 1) through disk manager (which defaults to dynamic disks) on an external disc enclosure, unplugging and then plugging the disc enclosure back in may cause the raid configuration be lost. 


Dynamic Disks was designed without consideration for removable drives. As this technology is older it was made obsolete in Windows 8. However, Dynamic Disks still exists in Windows 8 for backward compatibility. 


If you have created a dynamic disk mirror set, you have then unplugged the mirror, and now have a broken mirror, you should still be able to access your data from the device. By using Storage Spaces, included in Windows 8 and later versions, to create a mirror set, you will not encounter this issue. 
Note: Storage Spaces is unavailable on Windows 7.

More Information

This issue was observed in external USB disk enclosures with more than 1 hard disc drive and motherboards that support Thunderbolt connected devices.