Hi QianWang-7847,
There may be alignment issues plus disk controller compatibility. I'd recommend asking the disk controller manufacturer about this and specifically the disks in use.
I have done the following in the past and it has worked for me:
Switch the RAID to Spanned Volume. Then delete this volume and set to mirror on the two disks empty disks. I then had a functioning mirror again on the two disks. Make sure you back up any data before switching the spanned and deleting the RAID.
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