Or lack of.
You must insure that your drives are using the sata driver (if they are sata disks), quickest way to check is that they will be called sda sdb etc…. and not hda hdb, as this is the default IDE driver and will slow down the performance majorly.
How to check performance;
hdparm -tT /dev/hda
Modern drives should be getting over 50MB/s easily. If your getting about 5MB/s you have the problem.
How to Fix;
I had to change the sata mode to Enhanced in the bios and disable any of the on-board IDE controllers. When rebooting all your device names will change, and you will need to edit the /etc/fstab file as appropriate.
Apparently this is due to a conflict in the drivers, and them confusing your SATA drives as standard IDE disks.