Sure it*s possible...
Safest bet is probably the following sequence (if your RAIDs run on real RAID controller):
- stop all database services, (and perhaps make sure they don't start again at reboot for very safe)
- (very safe option: start system with independent Windows medium)
- insert the two new disks, and create a new RAID1
- copy all data from "old" second RAID1 to "new" (temporarily third) RAID1
- (very safe option: start system from first RAID1)
- change drive letters for the two RAID1 sets (assuming your M$ SQL runs in Windows) so that the "new" RAID1 gets the drive letter of the "old" RAID1
- start database services (and set them back to automatic start if necessary)
- optional: Decomission (or re-format) filesystem on "old" RAID1 or remove the disks
NB: If there's no room for the additional two disks in your RX200s5 housing, or your RAID controller does not support a third Virtual Drive, you need to store away the data from your second RAID1 to external media, remove the disks for the second RAID1, insert the new bigger drives and create a RAID1 on them, finally restore data from external media. Benefit: You have a backup of your data on external media.
Need to be quicker