Hello. You can use an old drive to replace the failed drive. Once prompted, clear the foreign configuration and the drive should be able to rebuild automatically. If it does not rebuild, assign it as Hot Spare to initiate the rebuild process. Thank you.
I did search the internet a lot with no results but after I posted I saw a post similar to mine on here.  The RAID 5 is rebuilding automatically.  Thanks!   Original post I have a failed disk in a RAID 5.  I have a used disk from another server no longer in use.  Would it be recommended to use it?  This is a older outdated server with no support.  Unfortunately I have not upgraded it yet.  Dell no longer sells the parts for it. Will the rebuild of the RAID start once the disk is swapped?  Thanks.
Update - I am rebuilding (RAID 5 - Rebuild with a used disk?)