I'm not familiar with the capabilities of the RAID controller which you are using, but can you confirm that it mirrored the data to the second (added) disk after reconfiguring the RAID from 0 to 1? Assuming the mirroring worked, do some checks to see how things look like.
- Check whether the newly create RAID1 LUN has been detected as a snapshot LUN (see "Command line" section at https://kb.vmware.com/s/article/1011387)
- Run the partetUtil getptbl ... command, as well as the command in step 1 of https://kb.vmware.com/s/article/2046610 to see whether it shows the expected output
- post the output of ls -elisa for the contents of /vmfs/volumes