RAID-1 fails when moving files out of disk

I am using Windows 7 x64, and have an SSD as my OS drive (C:) and a RAID-1 on (D:). I want to backup my files in D:, so I am trying to copy-paste its files onto another drive. Initially, I wanted to move them to an exteal HDD. While doing this, after a while, Intel Rapid Storage Technology (RST) displays a flag, saying one of the disks has failed. As can be read in the link above, if the copy-pasting continues, my RAID fails and after Windows reboots, D: is gone. Now I have connected an inteal HDD via SATA to my PC, and attempted the same: copy-paste the files from D: into my new HDD (E:). Unsurprisingly, Intel RST displayed an error once again.

In short, moving files out of my D: drive seems to "break" my RAID-1 setup (or it seems to alter Intel RST somehow). How can I backup these files ASAP?

Thank you!

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