We have here older MBs with two SATA-channels only.
1.Quick Data-backup(huge data)
a) using a second drive on slot 2.
b) using eSATA via 3SATA-adapter externally

If the old MB is slow then a) and b) will always have the same speed, right?
c) We can then eigher use a dockstation or external esata-case, right?
I have found these informations about esata versus usb3.
http://www.theregister.co.uk/2009/03/20/usb3_esata/
thanks a lot