I am running a homemade NAS using Ubuntu 10.04. I have 4 2TB hard drives in a RAID 10 setup - a stripe of mirrors.
Yesterday when accessing the data remotely, I got an I/O device error. When I logged into the machine and checked the disk utility, the RAID array state says "DEGRADED" and one of the drives' SMART status says "DISK FAILURE IMMINENT". One of the other disks has a few bad sectors, but its status is green and the other two drives are fine. Is it normal that I can't access any of the data in its current state? I feel like I should be able to access at least half but no transfers work from the RAID array.
How do I recover from this without losing any data? I called Western Digital and they are sending me a replacement drive in advance. Is it as easy as removing the failing drive and connected the new drive, then rebuilding the array? I have had trouble finding a good easy guide on Google and I don't want to lose this data - I am using RAID for a reason.