This question already has an answer here:
I want to exchange a Harddrive which is in a pre-failing state, (some reallocated sectors)
which is used in a raid5 array with 3 disks (software raid with
Is it possible to set a new harddrive as a hot-spare and initialize a takeover from the failing to the spare drive?
Some methods suggest to add the drive and then set a drive failure command. As I know, in this state the raid5 is degraded and a drive failure would end up in....
so is there a possibility to "copy" the data live (or rebuild the raid) from the failing drive to the spare (without take its parity function away), and as the copy or rebuild process is finished, remove the failing drive.