What is the procedure to replace a failing hard drive in a RAID array?

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http://serverfault.com – 3 years ago a co-worker setup a software RAID-6 array on Ubuntu 9.04 and I'm getting messages from the OS that the drive has bad sectors and should be replaced. I'd like to remove this drive and replace it with a new drive, however, I have never done this before and I'm terrified that in the process of fixing the array I'm going to end up ruining it. I know the device ID of the array and I know the device IDs of the individual drives in the array. Additionally I physically have the bad drive. What are the steps to replace the bad drive with a new drive and get the array running again? (HowTos)