Thanks for your replies, just to clear things up, here is what I am seeing. If I reboot server "A" with the Ubuntu LiveCD, I get: ---------------------------------------- # parted /dev/sda p Model: DELL PERC 5/i (scsi) Disk /dev/sda: 2998GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 32.3kB 53.7GB 53.7GB primary ext3 2 53.7GB 62.3GB 8595MB primary linux-swap 3 62.3GB 83.8GB 21.5GB primary ext3 4 83.8GB 2199GB 2115GB primary xfs # fdisk -l Disk /dev/sda: 2998.4 GB, 2998424043520 bytes 255 heads, 63 sectors/track, 364537 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x852b68e5 Device Boot Start End Blocks Id System /dev/sda1 1 6528 52436128+ 83 Linux /dev/sda2 6529 7573 8393962+ 82 Linux swap / Solaris /dev/sda3 7574 10185 20980890 83 Linux /dev/sda4 10186 267349 2065669830 83 Linux ---------------------------------------- Now when I try this with CentOS, I get: ---------------------------------------- Error: msdos labels do not support devices that have more than 4294967295 sectors. ----------------------------------------- straight away. I understand what you guys are saying about GPT and not being able to boot off it, etc but how did I end up in this situation? And is this dangerous? I am thinking that if this is possible, why not try and setup the second server the same way? But it just feels wrong that Ubuntu allows this and if CentOS does not, there must be a good reason.