Any of them are "safe". 1) There are many reasons that might prevent the disk from automatically rebuilding, so if it doesn't rebuild automatically, without OMSA, you'll need one of the other methods to Clear its foreign config and/or assign it as a hot-spare to start the rebuild. Just make sure you insert the disk "hot" (don't power down to replace it).
Sorry for the elementary question, but I'm happy to be looked upon as a simpleton if I can get it right.  :)  Error on LED is "E1810 HD 5 fault"  This disk is part of a RAID-1.  Machine is running CentOS 5.  OMSA is not installed. R510, 8 drive chassis.  Which is the recommended route to replacing the failed disk?  1) hot swap by pushing button, remove drive, install new drive, cross fingers, automatic rebuild?  2) Boot to Dell Support Live, run OMSA from that and do the replacement that way  3) Go into BIOS and do the replacement from there.  1) is the easiest if it will work, of course, but it's an important machine, so the safest way is the best.  Thanks very much for your time.  Cheers 
swap of failed drive on R510