If you encounter a situation where Windows only detects one of two NTFS drives connected simultaneously, despite both being physically connected, this might be due to identical disk signatures. This issue is common when one drive is cloned from another, resulting in identical identifiers.
Windows only detects one NTFS drive when two are connected
The issue arises because the disk signature (a unique identifier) is the same on both drives. Windows uses this signature to identify disks. When two drives share the same signature, Windows considers them the same disk, and only one is made available to avoid conflicts.
- Bring the Disk Online
- Change Disk Signature
1] Bring the Disk Online
- Open Computer Management and navigate to Storage > Disk Management. You can also use Disk Management directly using diskmgmt.msc in the run prompt.
- Check if both drives are listed. If one drive is offline, right-click it and select Online.
This should automatically assign a new ID to the disk, and there should not be any conflict.
2] Change Disk Signature
If the above doesn’t work; follow the steps to change the signature manually.
- Open Command Prompt as Administrator.
- Type
diskpartand press Enter to launch the DiskPart utility. - List all connected disks by typing:
list disk Identify the two disks (Disk 1 and Disk 2) based on their size.- Select Disk 2 (the one to modify) by typing:
select disk X - Replace
Xwith the number corresponding to Disk 2. - Display the current disk signature:
uniqueid disk Change the disk signature to a new unique value:uniqueid disk id=NEWID- Replace
NEWIDwith a hexadecimal value not already in use (e.g.,18329384). - If the disk is still offline, type the following command to bring it online: online disk
Close DiskPart and return to Disk Management. Both disks should now appear with unique identifiers and different letters.
Note: Using the diskpart command’s unique disk id= internal command is not necessary before setting the offline drive to online.
Read: How to find Disk and Volume GUID & List Volume GUIDs per Disk
Conclusion
The issue of Windows detecting only one drive stems from identical disk signatures. You can resolve the conflict by using DiskPart to assign a unique identifier to each drive and use both drives simultaneously.
What should I do if Windows doesn’t detect one of the drives even after assigning a unique disk signature?
If the issue persists, check Device Manager for driver issues, update your motherboard or docking station drivers, and run hardware diagnostics using tools. A failing drive or outdated drivers might cause detection problems.
Read: How to Copy or Clone Bootable USB Drive on Windows
Can identical disk signatures cause problems beyond detection in Windows?
Identical disk signatures can cause drive letter conflicts, boot errors, and software misidentifications during backups or cloning. Ensure they have unique signatures to prevent data corruption, system instability, and accidental overwrites, especially when handling cloned or previously duplicated drives.
