I have 4x2TB external hard drives in a raid5 configuration, and first I converted it to GPT disk using Disk Magagement in Windows 7. It shows basic disk, NTFS, 1 partition, 5.40TB, which is normal. It worked pretty well at first. But after copying files >2TB to this drive, some files were lost and cann't open. Once I unplug it and repulg it again. The system can't recognize it, and popped up a message "You need to format the disk...". Of course I don't want to format it! I checked it using Disk Management, it showed the drive in SAW (NOT NTFS). I plugged it into another laptop with same system, still can't recognize.
Then, I had no choise but to format it... copy again, and the same problem again!!! It takes me a whole week working on this. I still can't fix it, so... HELP ME!