How to prevent a drive turning to RAW file system
RAW file system normally exists in the transition state when the RAW partition has been already created but not yet formatted.
At this point there is no file system on the drive simply because it has not yet been created.
If you try to open the drive during that time, you see the message "Do you want to format it?"
This is normal. Just do not try to open the drive before the format completes.
External hard drives turn to RAW drives if they are disconnected from a computer without using a "Safely Remove Hardware" option.
This applies to memory cards as well, albeit to a lesser extent.
Always use "Safely remove hardware" to disconnect the drive.
Left click the icon on the taskbar, select the device from the menu, and wait for the confirmation message.
Some RAID controllers (What is RAID?)
change sector addressing on the connected drives.
If you connect such a drive to a different controller model on another computer, the drive appears damaged.
Conversely it is also true - if the drive is brought from the "normal" controller to a RAID one.
In such a case, a RAW file system issue can occur as well.
If this happens, you should connect the drive to the original place and copy the data off.
Always plan hard drive reassignments carefully. Make sure you have a current and tested backup before any major operation.
There are reported cases of malware causing the spurious RAW file system indications.
Once the malware is removed, the file system returns back to normal.
Make sure to use and update the antivirus software often.