When I switched on today my second hard drive I had the following issue displayed

The disk is offline because it has a signature collision with another disk that is online

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Running Diskpart as administrator proved that it was the issue

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As you can see disk 2 and disk 4 both have the 00024A91 signature hence the collision.

Following the advise here, I changed the signature of the drive decreasing from 1 unit.

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Than I brought back the disk online using Disk Management

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And everything went back to normal

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