In the event that a drive has failed, the first step is to make sure the drive is unmounted. This will make it easier for Object Storage to work around the failure until it has been resolved. If the drive is going to be replaced immediately, then it is just best to replace the drive, format it, remount it, and let replication fill it up.
If the drive can’t be replaced immediately, then it is best to leave it unmounted, and remove the drive from the ring. This will allow all the replicas that were on that drive to be replicated elsewhere until the drive is replaced. Once the drive is replaced, it can be re-added to the ring.
You can look at error messages in /var/log/kern.log for hints of drive failure.
