I found a SSD drive at work so i took it home to test it. The only machine i had that i could easily use was my NAS server. I have a 4TB mirror'd Raid 1 in it. I unplugged one of the drives and plugged in the SSD i found. Turns out the drive didn't work. So i plugged back in the 4TB drive and windows recognized it as a independant HD. I was afraid to delete the drive in disk manager and am now wondering if the raid array has been lost. I have over 2.5TB of data on the raid so i really would hate to lose it. Thoughts? The raid 1 was created using windows.

The data has not been lost on the first drive. All my data is in tact. However, the redundant drive now has partial folders from the primary drive. And windows now see's it as a independent drive. The purpose of a raid 1 is so that if 1 drive fails, you can plug in a new hard drive and the raid 1 will automatically transfer the data to the new drive. But in my case i did not have a drive failure. I just unplugged one of the drives and plugged in a test SSD. upon plugging back in the first drive, windows decided to see it as an independent drive and assigned it its own drive letter. Before i did this my raid 1 set showed as drive D: not drive D: and E:

  • Disk Mirror within Windows isn’t specifically RAID 1. Based on the behavior you describe there is a good chance your data is lost.
    – Ramhound
    Nov 21, 2019 at 19:59
  • More info has been added to the original post. Nov 21, 2019 at 21:21

1 Answer 1


Windows does not realize this disk is the same disk that was previously part of the array, for one reason or another. Generally you can fix this by un-assigning the drive letters, deleting any volumes on the removed drive, and re-adding it to the mirrors. We can do this using diskpart.

Warning: this is based on my best judgement and experience based on a limited view of your particular situation. Proceed with caution and stop and think twice if you encounter anything that doesn't seem to line up with the procedure described herein.

  1. Back up everything.
  2. Run diskpart as administrator (e.g. press Start, type "diskpart", press Ctrl-Shift-Enter)
  3. In diskpart: run list disk command. Identify with absolute certainty the number that represents the disk you are trying to get re-added to the array.
  4. select disk N where N is the number you identified.
  5. list volume and identify any drive letter(s) associated with any volume(s) on the disk.
  6. remove letter=X, replacing X with the drive letter in question, for each volume identified in the previous step.
  7. Delete the old volumes on the disk you are trying to re-add. Make absolutely sure you have identified the correct disk and volumes. For each volume, do select volume N then delete volume.
  8. Re-add the disk to the mirrored volumes. list volumes and identify which volume(s) are the mirrored volume(s) on your never-removed disk. For each such volume, select volume M, then add disk=N where M is the volume to be mirrored and N is your problematic disk.
  9. exit
  • You should also be able to do something like this in Windows' Disk Management GUI, although I'm not sure exactly what the procedure looks like doing it that way. You might consider at least glancing at the Disk Management tool if you haven't, as it may reveal additional information about your situation.
    – tgies
    Nov 21, 2019 at 22:48

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