Thank you all for your help! First of all my own server is running on 6.9.2 so using version 5 is the learning curve... not upgrading
I think I have all the information I need to do the upgrade so I feel a lot more confident.
But I do have another question. The server has an array of 5 4TB drives, 4 data drives and 1 parity. Disk 1 is disabled and needs to be replaced, I was going to do that after the upgrade but since it's quite a big upgrade I'm going to play it safe and replace drive 1 first. Disk 1 and 2 are used, 3 and 4 are empty. I was thinking of removing Disk 4 and use it to replace disk 1, however I read that after removing Disk 4 the parity needs to be rebuild which in my mind is tricky or impossible with a broken Disk 1.
Can I use 1 of the empty disks of the array to replace number 1? Or do I need to tell them to buy a new one?