Hello, I was put in charge of two servers which utilize RAID but I am not too knowledgeable about RAID. Mainly I'm just looking for peace of mind.
From what I understand, RAID 1 and 10 have fault tolerance and a disk can be replaced should it have issues. We have a Dell Poweredge 1800 with hardware RAID1 (Fedora) and another Dell server running software RAID10 via CentOS.
Thanks in advance.
1) My main concern right now is this: If a disk fails and I replace it, does it automatically know which disk is the new one? I wouldn't want it to overwrite the existing disk with the empty new one and end up with nothing. This server doesn't have hot-swap, so I'll have no choice but to power it down if/when I replace the drive.
2) If my RAID card fails and I have to get a new one, does it have to be an identical model? Will it auto-detect the drives and have everything work automatically?

Both the hardware RAID and software RAID operate similarly. They put a label on each disk so they know what is part of the RAID and what is not. The only time they could be confused is if you re-use a drive that already has RAID data on it. It's a good idea to overwrite the start and end few MB of a drive before using it in another system.

Software RAID will not use the new disk until you manually add it to the RAID using mdadm.

The hardware RAID card has a utility for managing RAID. If the hardware RAID card fails you need the same model, and may need the same firmware version if they have changed the on-disk metadata format. On the high-end RAID you would need to import the RAID set to a new controller. Not sure about the card-based RAID as I avoid them. The performance is generally not as good as software RAID and it has the single point of failure.

Thank you. Do you know of any step-by-step guides for repairing software RAID via mdadm? The OS itself is on the array.

EDIT: I found this which shouldn't be too different from CentOS: http://kamlau.com/software/how-to-re...raid-10-array/
Does it look good to you?

Also I also did a ddrescue to copy data from the RAID onto a single disk. Would it work if I copied it back the same way?