Maluco,   Not a silly question at all. If the drive is part of a raid 1, and hotswappable, then you should be able to just insert the replacement and it will automatically start rebuilding to the Virtual DIsk. Now in case it doesn't start automatically rebuilding, then you can go to the controller BIOS and configure the replacement drive as a hotspare, which will start the rebuild.   Let me know if this helps.  
Hello community! I have a Dell PowerEdge R610 (10 y-o) and recently we lost its operating system (Ubuntu) due a power outage. I thought this server had a striping (RAID0) configured but for my surprise, when I removed the HDD from tray 0, restarted the server and the operating system booted without any issues. The system is back. With this I'm assuming this server had RAID1 configure instead of RAID0. I bought a new disk (same part number) to replace the damaged disk (partition damage) and here is my question: Can I just plug back this newly bought disk (hot plug into the tray) and wait for the mirroring to work or should I configure something special to have RAID1 working as it was before? My apologies if this is a silly question. I'm no expert in servers or RAID whatsoever.
Replacing HDD on PowerEdge R610